diff --git a/README.md b/README.md
index b9dcbaf633..9cabb4c570 100644
--- a/README.md
+++ b/README.md
@@ -138,47 +138,47 @@ Stirling-PDF currently supports 40 languages!
 
 | Language                                     | Progress                               |
 |----------------------------------------------|----------------------------------------|
-| Arabic (العربية) (ar_AR)                     | ![66%](https://geps.dev/progress/66)   |
-| Azerbaijani (Azərbaycan Dili) (az_AZ)        | ![57%](https://geps.dev/progress/57)   |
-| Basque (Euskara) (eu_ES)                     | ![34%](https://geps.dev/progress/34)   |
-| Bulgarian (Български) (bg_BG)                | ![95%](https://geps.dev/progress/95)   |
-| Catalan (Català) (ca_CA)                     | ![62%](https://geps.dev/progress/62)   |
-| Croatian (Hrvatski) (hr_HR)                  | ![91%](https://geps.dev/progress/91)   |
-| Czech (Česky) (cs_CZ)                        | ![64%](https://geps.dev/progress/64)   |
-| Danish (Dansk) (da_DK)                       | ![57%](https://geps.dev/progress/57)   |
-| Dutch (Nederlands) (nl_NL)                   | ![89%](https://geps.dev/progress/89)   |
+| Arabic (العربية) (ar_AR)                     | ![58%](https://geps.dev/progress/58)   |
+| Azerbaijani (Azərbaycan Dili) (az_AZ)        | ![50%](https://geps.dev/progress/50)   |
+| Basque (Euskara) (eu_ES)                     | ![29%](https://geps.dev/progress/29)   |
+| Bulgarian (Български) (bg_BG)                | ![82%](https://geps.dev/progress/82)   |
+| Catalan (Català) (ca_CA)                     | ![54%](https://geps.dev/progress/54)   |
+| Croatian (Hrvatski) (hr_HR)                  | ![79%](https://geps.dev/progress/79)   |
+| Czech (Česky) (cs_CZ)                        | ![56%](https://geps.dev/progress/56)   |
+| Danish (Dansk) (da_DK)                       | ![49%](https://geps.dev/progress/49)   |
+| Dutch (Nederlands) (nl_NL)                   | ![78%](https://geps.dev/progress/78)   |
 | English (English) (en_GB)                    | ![100%](https://geps.dev/progress/100) |
 | English (US) (en_US)                         | ![100%](https://geps.dev/progress/100) |
-| French (Français) (fr_FR)                    | ![98%](https://geps.dev/progress/98)   |
-| German (Deutsch) (de_DE)                     | ![99%](https://geps.dev/progress/99)   |
-| Greek (Ελληνικά) (el_GR)                     | ![62%](https://geps.dev/progress/62)   |
-| Hindi (हिंदी) (hi_IN)                        | ![62%](https://geps.dev/progress/62)   |
-| Hungarian (Magyar) (hu_HU)                   | ![98%](https://geps.dev/progress/98)   |
-| Indonesian (Bahasa Indonesia) (id_ID)        | ![57%](https://geps.dev/progress/57)   |
-| Irish (Gaeilge) (ga_IE)                      | ![63%](https://geps.dev/progress/63)   |
-| Italian (Italiano) (it_IT)                   | ![96%](https://geps.dev/progress/96)   |
-| Japanese (日本語) (ja_JP)                       | ![90%](https://geps.dev/progress/90)   |
-| Korean (한국어) (ko_KR)                         | ![62%](https://geps.dev/progress/62)   |
-| Norwegian (Norsk) (no_NB)                    | ![61%](https://geps.dev/progress/61)   |
-| Persian (فارسی) (fa_IR)                      | ![59%](https://geps.dev/progress/59)   |
-| Polish (Polski) (pl_PL)                      | ![88%](https://geps.dev/progress/88)   |
-| Portuguese (Português) (pt_PT)               | ![87%](https://geps.dev/progress/87)   |
-| Portuguese Brazilian (Português) (pt_BR)     | ![84%](https://geps.dev/progress/84)   |
-| Romanian (Română) (ro_RO)                    | ![53%](https://geps.dev/progress/53)   |
-| Russian (Русский) (ru_RU)                    | ![89%](https://geps.dev/progress/89)   |
-| Serbian Latin alphabet (Srpski) (sr_LATN_RS) | ![92%](https://geps.dev/progress/92)   |
-| Simplified Chinese (简体中文) (zh_CN)            | ![86%](https://geps.dev/progress/86)   |
-| Slovakian (Slovensky) (sk_SK)                | ![47%](https://geps.dev/progress/47)   |
-| Slovenian (Slovenščina) (sl_SI)              | ![66%](https://geps.dev/progress/66)   |
-| Spanish (Español) (es_ES)                    | ![97%](https://geps.dev/progress/97)   |
-| Swedish (Svenska) (sv_SE)                    | ![60%](https://geps.dev/progress/60)   |
-| Thai (ไทย) (th_TH)                           | ![54%](https://geps.dev/progress/54)   |
-| Tibetan (བོད་ཡིག་) (bo_CN)                   | ![60%](https://geps.dev/progress/60)   |
-| Traditional Chinese (繁體中文) (zh_TW)           | ![95%](https://geps.dev/progress/95)   |
-| Turkish (Türkçe) (tr_TR)                     | ![92%](https://geps.dev/progress/92)   |
-| Ukrainian (Українська) (uk_UA)               | ![65%](https://geps.dev/progress/65)   |
-| Vietnamese (Tiếng Việt) (vi_VN)              | ![52%](https://geps.dev/progress/52)   |
-| Malayalam (മലയാളം) (ml_IN)                   | ![67%](https://geps.dev/progress/67)   |
+| French (Français) (fr_FR)                    | ![85%](https://geps.dev/progress/85)   |
+| German (Deutsch) (de_DE)                     | ![86%](https://geps.dev/progress/86)   |
+| Greek (Ελληνικά) (el_GR)                     | ![54%](https://geps.dev/progress/54)   |
+| Hindi (हिंदी) (hi_IN)                        | ![54%](https://geps.dev/progress/54)   |
+| Hungarian (Magyar) (hu_HU)                   | ![85%](https://geps.dev/progress/85)   |
+| Indonesian (Bahasa Indonesia) (id_ID)        | ![50%](https://geps.dev/progress/50)   |
+| Irish (Gaeilge) (ga_IE)                      | ![55%](https://geps.dev/progress/55)   |
+| Italian (Italiano) (it_IT)                   | ![85%](https://geps.dev/progress/85)   |
+| Japanese (日本語) (ja_JP)                       | ![79%](https://geps.dev/progress/79)   |
+| Korean (한국어) (ko_KR)                         | ![54%](https://geps.dev/progress/54)   |
+| Norwegian (Norsk) (no_NB)                    | ![53%](https://geps.dev/progress/53)   |
+| Persian (فارسی) (fa_IR)                      | ![52%](https://geps.dev/progress/52)   |
+| Polish (Polski) (pl_PL)                      | ![77%](https://geps.dev/progress/77)   |
+| Portuguese (Português) (pt_PT)               | ![76%](https://geps.dev/progress/76)   |
+| Portuguese Brazilian (Português) (pt_BR)     | ![74%](https://geps.dev/progress/74)   |
+| Romanian (Română) (ro_RO)                    | ![46%](https://geps.dev/progress/46)   |
+| Russian (Русский) (ru_RU)                    | ![91%](https://geps.dev/progress/91)   |
+| Serbian Latin alphabet (Srpski) (sr_LATN_RS) | ![80%](https://geps.dev/progress/80)   |
+| Simplified Chinese (简体中文) (zh_CN)            | ![75%](https://geps.dev/progress/75)   |
+| Slovakian (Slovensky) (sk_SK)                | ![41%](https://geps.dev/progress/41)   |
+| Slovenian (Slovenščina) (sl_SI)              | ![57%](https://geps.dev/progress/57)   |
+| Spanish (Español) (es_ES)                    | ![85%](https://geps.dev/progress/85)   |
+| Swedish (Svenska) (sv_SE)                    | ![52%](https://geps.dev/progress/52)   |
+| Thai (ไทย) (th_TH)                           | ![47%](https://geps.dev/progress/47)   |
+| Tibetan (བོད་ཡིག་) (bo_CN)                   | ![52%](https://geps.dev/progress/52)   |
+| Traditional Chinese (繁體中文) (zh_TW)           | ![82%](https://geps.dev/progress/82)   |
+| Turkish (Türkçe) (tr_TR)                     | ![80%](https://geps.dev/progress/80)   |
+| Ukrainian (Українська) (uk_UA)               | ![57%](https://geps.dev/progress/57)   |
+| Vietnamese (Tiếng Việt) (vi_VN)              | ![46%](https://geps.dev/progress/46)   |
+| Malayalam (മലയാളം) (ml_IN)                   | ![59%](https://geps.dev/progress/59)   |
 
 ## Stirling PDF Enterprise
 
diff --git a/app/core/src/main/resources/messages_ar_AR.properties b/app/core/src/main/resources/messages_ar_AR.properties
index 1dce60d581..b55db1120b 100644
--- a/app/core/src/main/resources/messages_ar_AR.properties
+++ b/app/core/src/main/resources/messages_ar_AR.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=لم يتم العثور على إشارات مرجع
 error.fontLoadingFailed=حدث خطأ أثناء معالجة ملف الخط
 error.fontDirectoryReadFailed=فشل في قراءة دليل الخطوط
 error.noAttachmentsFound=No embedded attachments were found in the provided PDF.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=حذف
 username=اسم المستخدم
 password=كلمة المرور
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF to CBZ
 home.pdfToCbz.desc=Convert PDF files to CBZ comic book archives.
 pdfToCbz.tags=conversion,comic,book,archive,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF to CBR
 pdfToCBR.header=PDF to CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF to Vector Image
 pdfToVector.description=Convert a PDF into Ghostscript-generated vector formats (EPS, PS, PCL, or XPS).
 pdfToVector.outputFormat=Output format
 pdfToVector.submit=Convert
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_az_AZ.properties b/app/core/src/main/resources/messages_az_AZ.properties
index 28d8528b0d..951eeedddf 100644
--- a/app/core/src/main/resources/messages_az_AZ.properties
+++ b/app/core/src/main/resources/messages_az_AZ.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=No PDF bookmarks/outline found in document
 error.fontLoadingFailed=Error processing font file
 error.fontDirectoryReadFailed=Failed to read font directory
 error.noAttachmentsFound=No embedded attachments were found in the provided PDF.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=Sil
 username=İstifadəçi Adı
 password=Şifr
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF to CBZ
 home.pdfToCbz.desc=Convert PDF files to CBZ comic book archives.
 pdfToCbz.tags=conversion,comic,book,archive,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF to CBR
 pdfToCBR.header=PDF to CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF to Vector Image
 pdfToVector.description=Convert a PDF into Ghostscript-generated vector formats (EPS, PS, PCL, or XPS).
 pdfToVector.outputFormat=Output format
 pdfToVector.submit=Convert
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_bg_BG.properties b/app/core/src/main/resources/messages_bg_BG.properties
index ac3f7d2fdf..965bcd5ece 100644
--- a/app/core/src/main/resources/messages_bg_BG.properties
+++ b/app/core/src/main/resources/messages_bg_BG.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=В документа не са намерени PDF
 error.fontLoadingFailed=Грешка при обработката на шрифтовия файл
 error.fontDirectoryReadFailed=Неуспешно четене на директорията с шрифтове
 error.noAttachmentsFound=В предоставения PDF файл не са намерени вградени прикачени файлове.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=Изтрий
 username=Потребителско име
 password=Парола
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF в CBZ
 home.pdfToCbz.desc=Преобразуване на PDF файлове в архиви на комикси на CBZ.
 pdfToCbz.tags=преобразуване,комикс,книга,архив,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF в CBR
 pdfToCBR.header=PDF в CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF във векторно изображение
 pdfToVector.description=Преобразуване на PDF файл в генерирани от Ghostscript векторни формати (EPS, PS, PCL или XPS).
 pdfToVector.outputFormat=Изходен формат
 pdfToVector.submit=Преобразуване
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_bo_CN.properties b/app/core/src/main/resources/messages_bo_CN.properties
index 0c9e4976bd..28a452c4e6 100644
--- a/app/core/src/main/resources/messages_bo_CN.properties
+++ b/app/core/src/main/resources/messages_bo_CN.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=No PDF bookmarks/outline found in document
 error.fontLoadingFailed=Error processing font file
 error.fontDirectoryReadFailed=Failed to read font directory
 error.noAttachmentsFound=No embedded attachments were found in the provided PDF.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=སུབ་པ།
 username=སྤྱོད་མཁན་མིང་།
 password=གསང་ཚིག།
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF to CBZ
 home.pdfToCbz.desc=Convert PDF files to CBZ comic book archives.
 pdfToCbz.tags=conversion,comic,book,archive,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF to CBR
 pdfToCBR.header=PDF to CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF to Vector Image
 pdfToVector.description=Convert a PDF into Ghostscript-generated vector formats (EPS, PS, PCL, or XPS).
 pdfToVector.outputFormat=Output format
 pdfToVector.submit=Convert
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_ca_CA.properties b/app/core/src/main/resources/messages_ca_CA.properties
index 36dcea7c21..2e1fa46578 100644
--- a/app/core/src/main/resources/messages_ca_CA.properties
+++ b/app/core/src/main/resources/messages_ca_CA.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=No PDF bookmarks/outline found in document
 error.fontLoadingFailed=Error processing font file
 error.fontDirectoryReadFailed=Failed to read font directory
 error.noAttachmentsFound=No embedded attachments were found in the provided PDF.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=Esborra
 username=Usuari
 password=Contrasenya
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF to CBZ
 home.pdfToCbz.desc=Convert PDF files to CBZ comic book archives.
 pdfToCbz.tags=conversion,comic,book,archive,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF to CBR
 pdfToCBR.header=PDF to CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF to Vector Image
 pdfToVector.description=Convert a PDF into Ghostscript-generated vector formats (EPS, PS, PCL, or XPS).
 pdfToVector.outputFormat=Output format
 pdfToVector.submit=Convert
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_cs_CZ.properties b/app/core/src/main/resources/messages_cs_CZ.properties
index b696285a58..8af9880a81 100644
--- a/app/core/src/main/resources/messages_cs_CZ.properties
+++ b/app/core/src/main/resources/messages_cs_CZ.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=No PDF bookmarks/outline found in document
 error.fontLoadingFailed=Error processing font file
 error.fontDirectoryReadFailed=Failed to read font directory
 error.noAttachmentsFound=No embedded attachments were found in the provided PDF.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=Smazat
 username=Uživatelské jméno
 password=Heslo
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF to CBZ
 home.pdfToCbz.desc=Convert PDF files to CBZ comic book archives.
 pdfToCbz.tags=conversion,comic,book,archive,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF to CBR
 pdfToCBR.header=PDF to CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF to Vector Image
 pdfToVector.description=Convert a PDF into Ghostscript-generated vector formats (EPS, PS, PCL, or XPS).
 pdfToVector.outputFormat=Output format
 pdfToVector.submit=Convert
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_da_DK.properties b/app/core/src/main/resources/messages_da_DK.properties
index 0ac2c4b0a8..ea3471bed4 100644
--- a/app/core/src/main/resources/messages_da_DK.properties
+++ b/app/core/src/main/resources/messages_da_DK.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=No PDF bookmarks/outline found in document
 error.fontLoadingFailed=Error processing font file
 error.fontDirectoryReadFailed=Failed to read font directory
 error.noAttachmentsFound=No embedded attachments were found in the provided PDF.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=Slet
 username=Brugernavn
 password=Adgangskode
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF to CBZ
 home.pdfToCbz.desc=Convert PDF files to CBZ comic book archives.
 pdfToCbz.tags=conversion,comic,book,archive,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF to CBR
 pdfToCBR.header=PDF to CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF to Vector Image
 pdfToVector.description=Convert a PDF into Ghostscript-generated vector formats (EPS, PS, PCL, or XPS).
 pdfToVector.outputFormat=Output format
 pdfToVector.submit=Convert
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_de_DE.properties b/app/core/src/main/resources/messages_de_DE.properties
index f65ca121f4..f531ecb165 100644
--- a/app/core/src/main/resources/messages_de_DE.properties
+++ b/app/core/src/main/resources/messages_de_DE.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=Keine PDF-Lesezeichen/Gliederung im Dokument gefunden
 error.fontLoadingFailed=Fehler bei der Verarbeitung der Schriftdatei.
 error.fontDirectoryReadFailed=Konnte das Schriftverzeichnis nicht lesen.
 error.noAttachmentsFound=Keine eingebetteten Anhänge im bereitgestellten PDF gefunden.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=Löschen
 username=Benutzername
 password=Passwort
@@ -620,6 +706,10 @@ home.ebookToPdf.title=E-Book zu PDF
 home.ebookToPdf.desc=E-Book-Dateien (EPUB, MOBI, AZW3, FB2, TXT, DOCX) mit Calibre in PDF konvertieren.
 ebookToPdf.tags=konvertierung,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF zu CBZ
 home.pdfToCbz.desc=PDF-Dateien in CBZ-Comicarchive umwandeln.
 pdfToCbz.tags=konvertierung,comic,buch,archiv,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Seitenzahlen zur erzeugten PDF hinzufügen
 ebookToPDF.optimizeForEbook=PDF für E-Book-Reader optimieren (verwendet Ghostscript)
 ebookToPDF.calibreDisabled=Calibre-Unterstützung ist deaktiviert. Aktivieren Sie die Calibre-Werkzeuggruppe oder installieren Sie Calibre, um diese Funktion zu nutzen.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF zu CBR
 pdfToCBR.header=PDF zu CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF zu Vektorgrafik
 pdfToVector.description=Konvertieren Sie ein PDF in Ghostscript-generierte Vektorformate (EPS, PS, PCL oder XPS).
 pdfToVector.outputFormat=Ausgabeformat
 pdfToVector.submit=Konvertieren
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_el_GR.properties b/app/core/src/main/resources/messages_el_GR.properties
index 19602622ea..751d6d62e3 100644
--- a/app/core/src/main/resources/messages_el_GR.properties
+++ b/app/core/src/main/resources/messages_el_GR.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=No PDF bookmarks/outline found in document
 error.fontLoadingFailed=Error processing font file
 error.fontDirectoryReadFailed=Failed to read font directory
 error.noAttachmentsFound=No embedded attachments were found in the provided PDF.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=Διαγραφή
 username=Όνομα χρήστη
 password=Κωδικός
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF to CBZ
 home.pdfToCbz.desc=Convert PDF files to CBZ comic book archives.
 pdfToCbz.tags=conversion,comic,book,archive,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF to CBR
 pdfToCBR.header=PDF to CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF to Vector Image
 pdfToVector.description=Convert a PDF into Ghostscript-generated vector formats (EPS, PS, PCL, or XPS).
 pdfToVector.outputFormat=Output format
 pdfToVector.submit=Convert
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_en_US.properties b/app/core/src/main/resources/messages_en_US.properties
index eb48bf5676..53f41e911f 100644
--- a/app/core/src/main/resources/messages_en_US.properties
+++ b/app/core/src/main/resources/messages_en_US.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=No PDF bookmarks/outline found in document
 error.fontLoadingFailed=Error processing font file
 error.fontDirectoryReadFailed=Failed to read font directory
 error.noAttachmentsFound=No embedded attachments were found in the provided PDF.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=Delete
 username=Username
 password=Password
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF to CBZ
 home.pdfToCbz.desc=Convert PDF files to CBZ comic book archives.
 pdfToCbz.tags=conversion,comic,book,archive,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF to CBR
 pdfToCBR.header=PDF to CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF to Vector Image
 pdfToVector.description=Convert a PDF into Ghostscript-generated vector formats (EPS, PS, PCL, or XPS).
 pdfToVector.outputFormat=Output format
 pdfToVector.submit=Convert
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_es_ES.properties b/app/core/src/main/resources/messages_es_ES.properties
index e9b0cf4ea6..1c32ab2471 100644
--- a/app/core/src/main/resources/messages_es_ES.properties
+++ b/app/core/src/main/resources/messages_es_ES.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=No se encontraron marcadores/esquemas en el documento
 error.fontLoadingFailed=Error al procesar el archivo de fuente
 error.fontDirectoryReadFailed=Error al leer el directorio de fuentes
 error.noAttachmentsFound=No se encontraron archivos adjuntos en el PDF proporcionado.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=Borrar
 username=Nombre de usuario
 password=Contraseña
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF a CBZ
 home.pdfToCbz.desc=Convierte archivos PDF a formato cómics CBZ.
 pdfToCbz.tags=conversion,comic,book,archive,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF a CBR
 pdfToCBR.header=PDF a CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF a imagen vectorial
 pdfToVector.description=Convertir un PDF a formatos vectoriales generados por Ghostscript (EPS, PS, PCL o XPS).
 pdfToVector.outputFormat=Formato de salida
 pdfToVector.submit=Convertir
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_eu_ES.properties b/app/core/src/main/resources/messages_eu_ES.properties
index 4bb4a17edc..d6145be68b 100644
--- a/app/core/src/main/resources/messages_eu_ES.properties
+++ b/app/core/src/main/resources/messages_eu_ES.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=No PDF bookmarks/outline found in document
 error.fontLoadingFailed=Error processing font file
 error.fontDirectoryReadFailed=Failed to read font directory
 error.noAttachmentsFound=No embedded attachments were found in the provided PDF.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=ezabatu
 username=Erabiltzaile izena
 password=Pasahitza
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF to CBZ
 home.pdfToCbz.desc=Convert PDF files to CBZ comic book archives.
 pdfToCbz.tags=conversion,comic,book,archive,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF to CBR
 pdfToCBR.header=PDF to CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF to Vector Image
 pdfToVector.description=Convert a PDF into Ghostscript-generated vector formats (EPS, PS, PCL, or XPS).
 pdfToVector.outputFormat=Output format
 pdfToVector.submit=Convert
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_fa_IR.properties b/app/core/src/main/resources/messages_fa_IR.properties
index 0f3e28d27d..a112ad303f 100644
--- a/app/core/src/main/resources/messages_fa_IR.properties
+++ b/app/core/src/main/resources/messages_fa_IR.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=No PDF bookmarks/outline found in document
 error.fontLoadingFailed=Error processing font file
 error.fontDirectoryReadFailed=Failed to read font directory
 error.noAttachmentsFound=No embedded attachments were found in the provided PDF.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=حذف
 username=نام کاربری
 password=رمز عبور
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF to CBZ
 home.pdfToCbz.desc=Convert PDF files to CBZ comic book archives.
 pdfToCbz.tags=conversion,comic,book,archive,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF to CBR
 pdfToCBR.header=PDF to CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF to Vector Image
 pdfToVector.description=Convert a PDF into Ghostscript-generated vector formats (EPS, PS, PCL, or XPS).
 pdfToVector.outputFormat=Output format
 pdfToVector.submit=Convert
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_fr_FR.properties b/app/core/src/main/resources/messages_fr_FR.properties
index 7711764ff4..54bd21301c 100644
--- a/app/core/src/main/resources/messages_fr_FR.properties
+++ b/app/core/src/main/resources/messages_fr_FR.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=Aucun signet ou plan PDF trouvé dans le document
 error.fontLoadingFailed=Erreur lors du traitement du fichier de police
 error.fontDirectoryReadFailed=Échec de la lecture du répertoire de polices
 error.noAttachmentsFound=Aucune pièce-jointe embarqué n'a été trouvé dans le PDF fourni.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=Supprimer
 username=Nom d'utilisateur
 password=Mot de passe
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF en CBZ
 home.pdfToCbz.desc=Convertissez un fichier PDF en archive de bande dessinée CBZ.
 pdfToCbz.tags=bande dessinée,convertir,conversion,comic,book,archive,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF en CBR
 pdfToCBR.header=PDF en CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF en image vectorielle
 pdfToVector.description=Convertissez un fichier PDF en formats vectoriels générés par Ghostscript (EPS, PS, PCL ou XPS).
 pdfToVector.outputFormat=Format de sortie
 pdfToVector.submit=Convertir
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_ga_IE.properties b/app/core/src/main/resources/messages_ga_IE.properties
index ef834f08ed..712819dc68 100644
--- a/app/core/src/main/resources/messages_ga_IE.properties
+++ b/app/core/src/main/resources/messages_ga_IE.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=No PDF bookmarks/outline found in document
 error.fontLoadingFailed=Error processing font file
 error.fontDirectoryReadFailed=Failed to read font directory
 error.noAttachmentsFound=No embedded attachments were found in the provided PDF.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=Scrios
 username=Ainm úsáideora
 password=Pasfhocal
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF to CBZ
 home.pdfToCbz.desc=Convert PDF files to CBZ comic book archives.
 pdfToCbz.tags=conversion,comic,book,archive,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF to CBR
 pdfToCBR.header=PDF to CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF to Vector Image
 pdfToVector.description=Convert a PDF into Ghostscript-generated vector formats (EPS, PS, PCL, or XPS).
 pdfToVector.outputFormat=Output format
 pdfToVector.submit=Convert
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_hi_IN.properties b/app/core/src/main/resources/messages_hi_IN.properties
index e5441d3610..ff5a1109c5 100644
--- a/app/core/src/main/resources/messages_hi_IN.properties
+++ b/app/core/src/main/resources/messages_hi_IN.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=No PDF bookmarks/outline found in document
 error.fontLoadingFailed=Error processing font file
 error.fontDirectoryReadFailed=Failed to read font directory
 error.noAttachmentsFound=No embedded attachments were found in the provided PDF.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=हटाएं
 username=उपयोगकर्ता नाम
 password=पासवर्ड
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF to CBZ
 home.pdfToCbz.desc=Convert PDF files to CBZ comic book archives.
 pdfToCbz.tags=conversion,comic,book,archive,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF to CBR
 pdfToCBR.header=PDF to CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF to Vector Image
 pdfToVector.description=Convert a PDF into Ghostscript-generated vector formats (EPS, PS, PCL, or XPS).
 pdfToVector.outputFormat=Output format
 pdfToVector.submit=Convert
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_hr_HR.properties b/app/core/src/main/resources/messages_hr_HR.properties
index 88ea500094..a13139e905 100644
--- a/app/core/src/main/resources/messages_hr_HR.properties
+++ b/app/core/src/main/resources/messages_hr_HR.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=U dokumentu nisu pronađene PDF oznake/sadržaj
 error.fontLoadingFailed=Pogreška pri obradi datoteke fonta
 error.fontDirectoryReadFailed=Čitanje direktorija fontova nije uspjelo
 error.noAttachmentsFound=No embedded attachments were found in the provided PDF.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=Izbriši
 username=Korisničko ime
 password=Lozinka
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF to CBZ
 home.pdfToCbz.desc=Convert PDF files to CBZ comic book archives.
 pdfToCbz.tags=conversion,comic,book,archive,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF to CBR
 pdfToCBR.header=PDF to CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF to Vector Image
 pdfToVector.description=Convert a PDF into Ghostscript-generated vector formats (EPS, PS, PCL, or XPS).
 pdfToVector.outputFormat=Output format
 pdfToVector.submit=Convert
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_hu_HU.properties b/app/core/src/main/resources/messages_hu_HU.properties
index f44aa6fe04..8b54c639ef 100644
--- a/app/core/src/main/resources/messages_hu_HU.properties
+++ b/app/core/src/main/resources/messages_hu_HU.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=Nem található PDF-könyvjelző/vázlat a dokumentum
 error.fontLoadingFailed=Hiba a betűtípusfájl feldolgozása közben
 error.fontDirectoryReadFailed=Nem sikerült beolvasni a betűtípus-könyvtárat
 error.noAttachmentsFound=A megadott PDF-ben nem találhatók beágyazott mellékletek.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=Törlés
 username=Felhasználónév
 password=Jelszó
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF konvertálása CBZ-be
 home.pdfToCbz.desc=PDF fájlok konvertálása CBZ képregény archívumokba.
 pdfToCbz.tags=konverzió,képregény,könyv,archívum,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF konvertálása CBR-be
 pdfToCBR.header=PDF konvertálása CBR-be
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF konvertálása vektorgrafikává
 pdfToVector.description=PDF konvertálása Ghostscript által létrehozott vektoros formátumokra (EPS, PS, PCL vagy XPS).
 pdfToVector.outputFormat=Kimeneti formátum
 pdfToVector.submit=Konvertálás
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_id_ID.properties b/app/core/src/main/resources/messages_id_ID.properties
index f984057bae..cced52d61e 100644
--- a/app/core/src/main/resources/messages_id_ID.properties
+++ b/app/core/src/main/resources/messages_id_ID.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=No PDF bookmarks/outline found in document
 error.fontLoadingFailed=Error processing font file
 error.fontDirectoryReadFailed=Failed to read font directory
 error.noAttachmentsFound=No embedded attachments were found in the provided PDF.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=Hapus
 username=Nama pengguna
 password=Kata sandi
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF to CBZ
 home.pdfToCbz.desc=Convert PDF files to CBZ comic book archives.
 pdfToCbz.tags=conversion,comic,book,archive,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF to CBR
 pdfToCBR.header=PDF to CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF to Vector Image
 pdfToVector.description=Convert a PDF into Ghostscript-generated vector formats (EPS, PS, PCL, or XPS).
 pdfToVector.outputFormat=Output format
 pdfToVector.submit=Convert
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_it_IT.properties b/app/core/src/main/resources/messages_it_IT.properties
index 7b2c22aa62..1d179ce87d 100644
--- a/app/core/src/main/resources/messages_it_IT.properties
+++ b/app/core/src/main/resources/messages_it_IT.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=Nessun segnalibro/schema PDF trovato nel documento
 error.fontLoadingFailed=Errore durante l'elaborazione del font file
 error.fontDirectoryReadFailed=Impossibile leggere la directory dei font
 error.noAttachmentsFound=Nessun allegato incorporato trovato nel PDF fornito.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=Elimina
 username=Nome utente
 password=Password
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook in PDF
 home.ebookToPdf.desc=Converti i file eBook (EPUB, MOBI, AZW3, FB2, TXT, DOCX) in PDF utilizzando Calibre.
 ebookToPdf.tags=conversione,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF in CBZ
 home.pdfToCbz.desc=Converti i file PDF negli archivi di fumetti CBZ.
 pdfToCbz.tags=conversione,fumetto,libro,archivio,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Aggiungere i numeri di pagina al PDF generato
 ebookToPDF.optimizeForEbook=Ottimizzazione PDF per lettori di ebook (utilizza Ghostscript)
 ebookToPDF.calibreDisabled=Il supporto di Calibre è disabilitato. Abilita il gruppo di strumenti Calibre o installa Calibre per utilizzare questa funzionalità.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF in CBR
 pdfToCBR.header=PDF in CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF in Immagine Vettoriale
 pdfToVector.description=Converti un PDF in formati vettoriali generati da Ghostscript (EPS, PS, PCL o XPS).
 pdfToVector.outputFormat=Formato di output
 pdfToVector.submit=Converti
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_ja_JP.properties b/app/core/src/main/resources/messages_ja_JP.properties
index 409a5ca49e..531b1feef2 100644
--- a/app/core/src/main/resources/messages_ja_JP.properties
+++ b/app/core/src/main/resources/messages_ja_JP.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=ドキュメント内にしおり/アウトライン
 error.fontLoadingFailed=フォントファイルの処理中にエラーが発生しました
 error.fontDirectoryReadFailed=フォントディレクトリの読み取りに失敗しました
 error.noAttachmentsFound=No embedded attachments were found in the provided PDF.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=削除
 username=ユーザー名
 password=パスワード
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDFをCBZに変換
 home.pdfToCbz.desc=PDFファイルをCBZコミックブックアーカイブに変換します。
 pdfToCbz.tags=conversion,comic,book,archive,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDFをCBRに変換
 pdfToCBR.header=PDFをCBRに変換
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF to Vector Image
 pdfToVector.description=Convert a PDF into Ghostscript-generated vector formats (EPS, PS, PCL, or XPS).
 pdfToVector.outputFormat=Output format
 pdfToVector.submit=Convert
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_ko_KR.properties b/app/core/src/main/resources/messages_ko_KR.properties
index aee2579e07..b16735973c 100644
--- a/app/core/src/main/resources/messages_ko_KR.properties
+++ b/app/core/src/main/resources/messages_ko_KR.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=No PDF bookmarks/outline found in document
 error.fontLoadingFailed=Error processing font file
 error.fontDirectoryReadFailed=Failed to read font directory
 error.noAttachmentsFound=No embedded attachments were found in the provided PDF.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=삭제
 username=사용자 이름
 password=비밀번호
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF to CBZ
 home.pdfToCbz.desc=Convert PDF files to CBZ comic book archives.
 pdfToCbz.tags=conversion,comic,book,archive,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF to CBR
 pdfToCBR.header=PDF to CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF to Vector Image
 pdfToVector.description=Convert a PDF into Ghostscript-generated vector formats (EPS, PS, PCL, or XPS).
 pdfToVector.outputFormat=Output format
 pdfToVector.submit=Convert
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_ml_IN.properties b/app/core/src/main/resources/messages_ml_IN.properties
index 398ce63e43..8a50b88046 100644
--- a/app/core/src/main/resources/messages_ml_IN.properties
+++ b/app/core/src/main/resources/messages_ml_IN.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=No PDF bookmarks/outline found in document
 error.fontLoadingFailed=Error processing font file
 error.fontDirectoryReadFailed=Failed to read font directory
 error.noAttachmentsFound=No embedded attachments were found in the provided PDF.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=മായ്ക്കുക
 username=ഉപയോക്തൃനാമം
 password=പാസ്വേഡ്
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF to CBZ
 home.pdfToCbz.desc=Convert PDF files to CBZ comic book archives.
 pdfToCbz.tags=conversion,comic,book,archive,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF to CBR
 pdfToCBR.header=PDF to CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF to Vector Image
 pdfToVector.description=Convert a PDF into Ghostscript-generated vector formats (EPS, PS, PCL, or XPS).
 pdfToVector.outputFormat=Output format
 pdfToVector.submit=Convert
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_nl_NL.properties b/app/core/src/main/resources/messages_nl_NL.properties
index 7504d9fb10..e1021208ce 100644
--- a/app/core/src/main/resources/messages_nl_NL.properties
+++ b/app/core/src/main/resources/messages_nl_NL.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=Geen bladwijzers/samenvatting aangetroffen in PDF-doc
 error.fontLoadingFailed=Fout bij het verwerken van lettertypebestand
 error.fontDirectoryReadFailed=Lezen van lettertypemap is mislukt
 error.noAttachmentsFound=Er zijn geen ingesloten bijlagen gevonden in de PDF.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=Verwijderen
 username=Gebruikersnaam
 password=Wachtwoord
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF naar CBZ
 home.pdfToCbz.desc=Converteer PDF-bestanden naar CBZ comic book archives.
 pdfToCbz.tags=conversie,comic,book,strip,album,archief,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF naar CBR
 pdfToCBR.header=PDF naar CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF naar vectorafbeelding
 pdfToVector.description=Converteer een PDF naar Ghostscript-gegenereerde vectorformaten (EPS, PS, PCL, of XPS).
 pdfToVector.outputFormat=Uitvoerformaat
 pdfToVector.submit=Converteren
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_no_NB.properties b/app/core/src/main/resources/messages_no_NB.properties
index e9564595f9..b01ae5cb05 100644
--- a/app/core/src/main/resources/messages_no_NB.properties
+++ b/app/core/src/main/resources/messages_no_NB.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=No PDF bookmarks/outline found in document
 error.fontLoadingFailed=Error processing font file
 error.fontDirectoryReadFailed=Failed to read font directory
 error.noAttachmentsFound=No embedded attachments were found in the provided PDF.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=Slett
 username=Brukernavn
 password=Passord
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF to CBZ
 home.pdfToCbz.desc=Convert PDF files to CBZ comic book archives.
 pdfToCbz.tags=conversion,comic,book,archive,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF to CBR
 pdfToCBR.header=PDF to CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF to Vector Image
 pdfToVector.description=Convert a PDF into Ghostscript-generated vector formats (EPS, PS, PCL, or XPS).
 pdfToVector.outputFormat=Output format
 pdfToVector.submit=Convert
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_pl_PL.properties b/app/core/src/main/resources/messages_pl_PL.properties
index 8457a46f4a..b983b8098f 100644
--- a/app/core/src/main/resources/messages_pl_PL.properties
+++ b/app/core/src/main/resources/messages_pl_PL.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=Nie znaleziono zakładek/struktury w dokumencie PDF
 error.fontLoadingFailed=Błąd podczas przetwarzania pliku czcionki
 error.fontDirectoryReadFailed=Nie udało się odczytać katalogu czcionek
 error.noAttachmentsFound=Nie znaleziono załączników w dokumencie PDF.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=usuń
 username=nazwa użytkownika
 password=hasło
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF na CBZ
 home.pdfToCbz.desc=Konwertuj pliki PDF na archiwa komiksów CBZ.
 pdfToCbz.tags=konwersja,komiks,książka,archiwum,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF na CBR
 pdfToCBR.header=PDF na CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF na Obraz Wektorowy
 pdfToVector.description=Konwertuj plik PDF na formaty wektorowe generowane przez Ghostscript (EPS, PS, PCL lub XPS).
 pdfToVector.outputFormat=Format wyjściowy
 pdfToVector.submit=Konwertuj
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_pt_BR.properties b/app/core/src/main/resources/messages_pt_BR.properties
index 3d8b410e4f..6b075add97 100644
--- a/app/core/src/main/resources/messages_pt_BR.properties
+++ b/app/core/src/main/resources/messages_pt_BR.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=Nenhum marcador/esquema de PDF encontrado no document
 error.fontLoadingFailed=Erro ao processar a fonte do arquivo
 error.fontDirectoryReadFailed=Falha ao ler a fonte do diretório
 error.noAttachmentsFound=No embedded attachments were found in the provided PDF.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=Apagar
 username=Usuário
 password=Senha
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF to CBZ
 home.pdfToCbz.desc=Convert PDF files to CBZ comic book archives.
 pdfToCbz.tags=conversion,comic,book,archive,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF to CBR
 pdfToCBR.header=PDF to CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF to Vector Image
 pdfToVector.description=Convert a PDF into Ghostscript-generated vector formats (EPS, PS, PCL, or XPS).
 pdfToVector.outputFormat=Output format
 pdfToVector.submit=Convert
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_pt_PT.properties b/app/core/src/main/resources/messages_pt_PT.properties
index 1cf8102be8..c43940c3e8 100644
--- a/app/core/src/main/resources/messages_pt_PT.properties
+++ b/app/core/src/main/resources/messages_pt_PT.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=Não foram encontrados marcadores/índices PDF no doc
 error.fontLoadingFailed=Erro ao processar o arquivo de fonte
 error.fontDirectoryReadFailed=Falha ao ler o diretório de fontes
 error.noAttachmentsFound=Não foram encontrados anexos incorporados no PDF fornecido.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=Eliminar
 username=Nome de utilizador
 password=Palavra-passe
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF para CBZ
 home.pdfToCbz.desc=Converter ficheiros PDF para arquivos de banda desenhada CBZ.
 pdfToCbz.tags=conversão,banda desenhada,livro,arquivo,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF para CBR
 pdfToCBR.header=PDF para CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF to Vector Image
 pdfToVector.description=Convert a PDF into Ghostscript-generated vector formats (EPS, PS, PCL, or XPS).
 pdfToVector.outputFormat=Output format
 pdfToVector.submit=Convert
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_ro_RO.properties b/app/core/src/main/resources/messages_ro_RO.properties
index 6f04c182d7..26933ab979 100644
--- a/app/core/src/main/resources/messages_ro_RO.properties
+++ b/app/core/src/main/resources/messages_ro_RO.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=No PDF bookmarks/outline found in document
 error.fontLoadingFailed=Error processing font file
 error.fontDirectoryReadFailed=Failed to read font directory
 error.noAttachmentsFound=No embedded attachments were found in the provided PDF.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=Șterge
 username=Nume de utilizator
 password=Parolă
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF to CBZ
 home.pdfToCbz.desc=Convert PDF files to CBZ comic book archives.
 pdfToCbz.tags=conversion,comic,book,archive,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF to CBR
 pdfToCBR.header=PDF to CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF to Vector Image
 pdfToVector.description=Convert a PDF into Ghostscript-generated vector formats (EPS, PS, PCL, or XPS).
 pdfToVector.outputFormat=Output format
 pdfToVector.submit=Convert
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_ru_RU.properties b/app/core/src/main/resources/messages_ru_RU.properties
index a27a8d30b4..933cca84a8 100644
--- a/app/core/src/main/resources/messages_ru_RU.properties
+++ b/app/core/src/main/resources/messages_ru_RU.properties
@@ -706,6 +706,10 @@ home.ebookToPdf.title=eBook в PDF
 home.ebookToPdf.desc=Преобразование eBook файлов (EPUB, MOBI, AZW3, FB2, TXT, DOCX) в PDF используя Calibre.
 ebookToPdf.tags=конвертация,ebook,книга,calibre,epub,mobi,azw3,fb2
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF в CBZ
 home.pdfToCbz.desc=Конвертируйте PDF-файлы в архивы комиксов CBZ.
 pdfToCbz.tags=конвертация,комикс,книга,архив,cbz,pdf
@@ -1592,6 +1596,20 @@ ebookToPDF.includePageNumbers=Добавить номера страниц в г
 ebookToPDF.optimizeForEbook=Оптимизировать PDF для чтения электронных книг (используется Ghostscript)
 ebookToPDF.calibreDisabled=Поддержка Calibre отключена. Чтобы использовать эту функцию, включите группу инструментов Calibre или установите Calibre.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF в CBR
 pdfToCBR.header=PDF в CBR
@@ -2270,7 +2288,7 @@ error.E051.hint.3=Просмотрите аргументы командной 
 error.E051.action=Убедитесь, что Ghostscript установлен и команда выполняется успешно.
 error.E054.hint.1=Преобразуйте файлы EPS или PS в одностраничный PDF-файл, прежде чем повторить эту операцию.
 error.E054.hint.2=Экспортируйте каждую страницу по отдельности из приложения-автора, чтобы Ghostscript обрабатывал по одной странице за раз.
-error.E054.hint.3=Используйте инструмент «Преобразовать в PDF» для сглаживания изображений или применения дополнительных эффектов, затем повторите команду. 
+error.E054.hint.3=Используйте инструмент «Преобразовать в PDF» для сглаживания изображений или применения дополнительных эффектов, затем повторите команду.
 error.E054.action=Преобразуйте исходный файл в одностраничный документ (или PDF) и повторите операцию.
 
 error.E052.hint.1=Убедитесь, что qpdf установлен и находится в системной переменной PATH.
diff --git a/app/core/src/main/resources/messages_sk_SK.properties b/app/core/src/main/resources/messages_sk_SK.properties
index fb30633a51..4a80ec7d60 100644
--- a/app/core/src/main/resources/messages_sk_SK.properties
+++ b/app/core/src/main/resources/messages_sk_SK.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=No PDF bookmarks/outline found in document
 error.fontLoadingFailed=Error processing font file
 error.fontDirectoryReadFailed=Failed to read font directory
 error.noAttachmentsFound=No embedded attachments were found in the provided PDF.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=Vymazať
 username=Používateľské meno
 password=Heslo
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF to CBZ
 home.pdfToCbz.desc=Convert PDF files to CBZ comic book archives.
 pdfToCbz.tags=conversion,comic,book,archive,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF to CBR
 pdfToCBR.header=PDF to CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF to Vector Image
 pdfToVector.description=Convert a PDF into Ghostscript-generated vector formats (EPS, PS, PCL, or XPS).
 pdfToVector.outputFormat=Output format
 pdfToVector.submit=Convert
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_sl_SI.properties b/app/core/src/main/resources/messages_sl_SI.properties
index 0480d8f184..0e33f31850 100644
--- a/app/core/src/main/resources/messages_sl_SI.properties
+++ b/app/core/src/main/resources/messages_sl_SI.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=No PDF bookmarks/outline found in document
 error.fontLoadingFailed=Error processing font file
 error.fontDirectoryReadFailed=Failed to read font directory
 error.noAttachmentsFound=No embedded attachments were found in the provided PDF.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=Izbriši
 username=Uporabniško ime
 password=Geslo
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF to CBZ
 home.pdfToCbz.desc=Convert PDF files to CBZ comic book archives.
 pdfToCbz.tags=conversion,comic,book,archive,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF to CBR
 pdfToCBR.header=PDF to CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF to Vector Image
 pdfToVector.description=Convert a PDF into Ghostscript-generated vector formats (EPS, PS, PCL, or XPS).
 pdfToVector.outputFormat=Output format
 pdfToVector.submit=Convert
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_sr_LATN_RS.properties b/app/core/src/main/resources/messages_sr_LATN_RS.properties
index f530a80c58..e7e9fe8c72 100644
--- a/app/core/src/main/resources/messages_sr_LATN_RS.properties
+++ b/app/core/src/main/resources/messages_sr_LATN_RS.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=PDF dokument ne sadrži obeleživače/navigacioni sad
 error.fontLoadingFailed=Greška prilikom obrade fonta
 error.fontDirectoryReadFailed=Greška prilikom pristupa direktorijuma sa fontovima
 error.noAttachmentsFound=No embedded attachments were found in the provided PDF.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=Obriši
 username=Korisničko ime
 password=Lozinka
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF to CBZ
 home.pdfToCbz.desc=Convert PDF files to CBZ comic book archives.
 pdfToCbz.tags=conversion,comic,book,archive,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF to CBR
 pdfToCBR.header=PDF to CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF to Vector Image
 pdfToVector.description=Convert a PDF into Ghostscript-generated vector formats (EPS, PS, PCL, or XPS).
 pdfToVector.outputFormat=Output format
 pdfToVector.submit=Convert
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_sv_SE.properties b/app/core/src/main/resources/messages_sv_SE.properties
index b157060fb9..bb7afdb060 100644
--- a/app/core/src/main/resources/messages_sv_SE.properties
+++ b/app/core/src/main/resources/messages_sv_SE.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=No PDF bookmarks/outline found in document
 error.fontLoadingFailed=Error processing font file
 error.fontDirectoryReadFailed=Failed to read font directory
 error.noAttachmentsFound=No embedded attachments were found in the provided PDF.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=Radera
 username=Användarnamn
 password=Lösenord
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF to CBZ
 home.pdfToCbz.desc=Convert PDF files to CBZ comic book archives.
 pdfToCbz.tags=conversion,comic,book,archive,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF to CBR
 pdfToCBR.header=PDF to CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF to Vector Image
 pdfToVector.description=Convert a PDF into Ghostscript-generated vector formats (EPS, PS, PCL, or XPS).
 pdfToVector.outputFormat=Output format
 pdfToVector.submit=Convert
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_th_TH.properties b/app/core/src/main/resources/messages_th_TH.properties
index abc773aee1..175567832d 100644
--- a/app/core/src/main/resources/messages_th_TH.properties
+++ b/app/core/src/main/resources/messages_th_TH.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=No PDF bookmarks/outline found in document
 error.fontLoadingFailed=Error processing font file
 error.fontDirectoryReadFailed=Failed to read font directory
 error.noAttachmentsFound=No embedded attachments were found in the provided PDF.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=ลบ
 username=ชื่อผู้ใช้
 password=รหัสผ่าน
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF to CBZ
 home.pdfToCbz.desc=Convert PDF files to CBZ comic book archives.
 pdfToCbz.tags=conversion,comic,book,archive,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF to CBR
 pdfToCBR.header=PDF to CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF to Vector Image
 pdfToVector.description=Convert a PDF into Ghostscript-generated vector formats (EPS, PS, PCL, or XPS).
 pdfToVector.outputFormat=Output format
 pdfToVector.submit=Convert
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_tr_TR.properties b/app/core/src/main/resources/messages_tr_TR.properties
index bfa7ac9aed..6769a6481c 100644
--- a/app/core/src/main/resources/messages_tr_TR.properties
+++ b/app/core/src/main/resources/messages_tr_TR.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=Belgede herhangi bir PDF yer imi / içindekiler bulun
 error.fontLoadingFailed=Yazı tipi dosyası işlenirken hata oluştu
 error.fontDirectoryReadFailed=Yazı tipi dizini okunamadı
 error.noAttachmentsFound=No embedded attachments were found in the provided PDF.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=Sil
 username=Kullanıcı Adı
 password=Parola
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF to CBZ
 home.pdfToCbz.desc=Convert PDF files to CBZ comic book archives.
 pdfToCbz.tags=conversion,comic,book,archive,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF to CBR
 pdfToCBR.header=PDF to CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF to Vector Image
 pdfToVector.description=Convert a PDF into Ghostscript-generated vector formats (EPS, PS, PCL, or XPS).
 pdfToVector.outputFormat=Output format
 pdfToVector.submit=Convert
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_uk_UA.properties b/app/core/src/main/resources/messages_uk_UA.properties
index 6982e3a6ec..de5423d153 100644
--- a/app/core/src/main/resources/messages_uk_UA.properties
+++ b/app/core/src/main/resources/messages_uk_UA.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=No PDF bookmarks/outline found in document
 error.fontLoadingFailed=Error processing font file
 error.fontDirectoryReadFailed=Failed to read font directory
 error.noAttachmentsFound=No embedded attachments were found in the provided PDF.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=Видалити
 username=Ім'я користувача
 password=Пароль
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF to CBZ
 home.pdfToCbz.desc=Convert PDF files to CBZ comic book archives.
 pdfToCbz.tags=conversion,comic,book,archive,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF to CBR
 pdfToCBR.header=PDF to CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF to Vector Image
 pdfToVector.description=Convert a PDF into Ghostscript-generated vector formats (EPS, PS, PCL, or XPS).
 pdfToVector.outputFormat=Output format
 pdfToVector.submit=Convert
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_vi_VN.properties b/app/core/src/main/resources/messages_vi_VN.properties
index 03a7333493..8058f262d0 100644
--- a/app/core/src/main/resources/messages_vi_VN.properties
+++ b/app/core/src/main/resources/messages_vi_VN.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=No PDF bookmarks/outline found in document
 error.fontLoadingFailed=Error processing font file
 error.fontDirectoryReadFailed=Failed to read font directory
 error.noAttachmentsFound=No embedded attachments were found in the provided PDF.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=Xóa
 username=Tên người dùng
 password=Mật khẩu
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF to CBZ
 home.pdfToCbz.desc=Convert PDF files to CBZ comic book archives.
 pdfToCbz.tags=conversion,comic,book,archive,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF to CBR
 pdfToCBR.header=PDF to CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF to Vector Image
 pdfToVector.description=Convert a PDF into Ghostscript-generated vector formats (EPS, PS, PCL, or XPS).
 pdfToVector.outputFormat=Output format
 pdfToVector.submit=Convert
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_zh_CN.properties b/app/core/src/main/resources/messages_zh_CN.properties
index bdf206c911..4d204cf81f 100644
--- a/app/core/src/main/resources/messages_zh_CN.properties
+++ b/app/core/src/main/resources/messages_zh_CN.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=文档中没有找到PDF书签/大纲
 error.fontLoadingFailed=处理字体文件出错
 error.fontDirectoryReadFailed=无法读取字体目录
 error.noAttachmentsFound=No embedded attachments were found in the provided PDF.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=删除
 username=用户名
 password=密码
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF to CBZ
 home.pdfToCbz.desc=Convert PDF files to CBZ comic book archives.
 pdfToCbz.tags=conversion,comic,book,archive,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF to CBR
 pdfToCBR.header=PDF to CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF to Vector Image
 pdfToVector.description=Convert a PDF into Ghostscript-generated vector formats (EPS, PS, PCL, or XPS).
 pdfToVector.outputFormat=Output format
 pdfToVector.submit=Convert
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.
diff --git a/app/core/src/main/resources/messages_zh_TW.properties b/app/core/src/main/resources/messages_zh_TW.properties
index 650ed0e69b..7744c0137f 100644
--- a/app/core/src/main/resources/messages_zh_TW.properties
+++ b/app/core/src/main/resources/messages_zh_TW.properties
@@ -235,6 +235,92 @@ error.pdfBookmarksNotFound=在文件中找不到 PDF 書籤/大綱
 error.fontLoadingFailed=處理字型檔案時發生錯誤
 error.fontDirectoryReadFailed=讀取字型目錄失敗
 error.noAttachmentsFound=No embedded attachments were found in the provided PDF.
+error.nullArgument={0} must not be null
+error.invalidPageSize=Invalid page size format: {0}
+error.invalidComparator=Invalid comparator format: only 'greater', 'equal', and 'less' are supported
+
+# Error titles for GlobalExceptionHandler
+error.pdfPassword.title=PDF Password Required
+error.outOfMemoryDpi.title=Out of Memory - DPI Too High
+error.pdfCorrupted.title=PDF File Corrupted
+error.multiplePdfCorrupted=One or more PDF files appear to be corrupted or damaged. Please try using the 'Repair PDF' feature on each file first before attempting to merge them.
+error.pdfEncryption.title=PDF Encryption Error
+error.application.title=Application Error
+error.cbrFormat.title=Invalid CBR File Format
+error.cbzFormat.title=Invalid CBZ File Format
+error.emlFormat.title=Invalid EML File Format
+error.formatError.title=Invalid File Format
+error.validation.title=Request Validation Failed
+error.validation.detail=Validation failed
+error.missingParameter.title=Missing Request Parameter
+error.missingParameter.detail=Required parameter ''{0}'' of type ''{1}'' is missing
+error.missingFile.title=Missing File Upload
+error.missingFile.detail=Required file part ''{0}'' is missing
+error.fileTooLarge.title=File Too Large
+error.fileTooLarge.detail=File size exceeds maximum allowed limit of {0} MB
+error.fileTooLarge.detailUnknown=File size exceeds maximum allowed limit
+error.methodNotAllowed.title=HTTP Method Not Allowed
+error.methodNotAllowed.detail=HTTP method ''{0}'' is not supported for this endpoint. Supported methods: {1}
+error.unsupportedMediaType.title=Unsupported Media Type
+error.unsupportedMediaType.detail=Media type ''{0}'' is not supported. Supported media types: {1}
+error.malformedRequest.title=Malformed Request Body
+error.malformedRequest.detail=Malformed JSON request or invalid request body format
+error.malformedRequest.detailWithCause=Invalid request body: {0}
+error.notFound.title=Endpoint Not Found
+error.notFound.detail=No endpoint found for {0} {1}
+error.invalidArgument.title=Invalid Argument
+error.ioError.title=File Processing Error
+error.ioError.detail=An error occurred while processing the file
+error.unexpected.title=Internal Server Error
+error.unexpected=An unexpected error occurred. Please try again later.
+
+# PDF-related error messages from ErrorCode enum
+error.pdfNoPages=PDF file contains no pages
+error.notPdfFile=File must be in PDF format
+
+# CBR/CBZ error messages from ErrorCode enum
+error.cbrInvalidFormat=Invalid or corrupted CBR/RAR archive. The file may be corrupted, use an unsupported RAR format (RAR5+), encrypted, or may not be a valid RAR archive.
+error.cbrNoImages=No valid images found in the CBR file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbrFile=File must be a CBR or RAR archive
+error.cbzInvalidFormat=Invalid or corrupted CBZ/ZIP archive. The file may be empty, corrupted, or may not be a valid ZIP archive.
+error.cbzNoImages=No valid images found in the CBZ file. The archive may be empty, or all images may be corrupted or in unsupported formats.
+error.notCbzFile=File must be a CBZ or ZIP archive
+
+# EML error messages from ErrorCode enum
+error.emlEmpty=EML file is empty or null
+error.emlInvalidFormat=Invalid EML file format
+
+# File processing error messages from ErrorCode enum
+error.fileNullOrEmpty=File cannot be null or empty
+error.fileNoName=File must have a name
+error.imageReadError=Unable to read image from file: {0}
+
+# OCR error messages from ErrorCode enum
+error.ocrLanguageRequired=OCR language options are not specified
+error.ocrInvalidLanguages=Invalid OCR languages format: none of the selected languages are valid
+error.ocrToolsUnavailable=OCR tools are not installed
+error.ocrInvalidRenderType=Invalid OCR render type. Must be 'hocr' or 'sandwich'
+error.ocrProcessingFailed=OCRmyPDF failed with return code: {0}
+
+# Compression error messages from ErrorCode enum
+error.compressionOptions=Compression options are not specified (expected output size and optimise level)
+error.ghostscriptCompression=Ghostscript compression command failed
+error.ghostscriptCompression.title=Ghostscript Processing Error
+error.ghostscriptPageDrawing=Ghostscript could not render {0}. {1}
+error.ghostscriptDefaultDiagnostic=The source file contains content Ghostscript cannot render.
+error.qpdfCompression=QPDF command failed
+error.processingInterrupted={0} processing was interrupted
+
+# Conversion error messages from ErrorCode enum
+error.pdfaConversionFailed=PDF/A conversion failed
+error.htmlFileRequired=File must be in HTML or ZIP format
+error.pythonRequiredWebp=Python is required for WebP conversion
+error.ffmpegRequired=FFmpeg must be installed to convert PDFs to video. Install FFmpeg and ensure it is available on the system PATH.
+error.ffmpegRequired.title=FFmpeg Required
+
+# System error messages from ErrorCode enum
+error.md5Algorithm=MD5 algorithm not available
+error.outOfMemoryDpi=Out of memory or image-too-large error while rendering PDF page {0} at {1} DPI. This can occur when the resulting image exceeds Java's array/memory limits (e.g., NegativeArraySizeException). Please use a lower DPI value (recommended: 150 or less) or process the document in smaller chunks.
 delete=刪除
 username=使用者名稱
 password=密碼
@@ -620,6 +706,10 @@ home.ebookToPdf.title=eBook to PDF
 home.ebookToPdf.desc=Convert eBook files (EPUB, MOBI, AZW3, FB2, TXT, DOCX) to PDF using Calibre.
 ebookToPdf.tags=conversion,ebook,calibre,epub,mobi,azw3
 
+home.pdfToEpub.title=PDF to EPUB/AZW3
+home.pdfToEpub.desc=Convert PDF files into EPUB or AZW3 ebooks optimised for e-readers using Calibre.
+pdfToEpub.tags=conversion,ebook,epub,azw3,calibre
+
 home.pdfToCbz.title=PDF 轉 CBZ
 home.pdfToCbz.desc=將 PDF 檔案轉換為 CBZ 漫畫封存檔。
 pdfToCbz.tags=轉換,漫畫,書,封存,cbz,pdf
@@ -1506,6 +1596,20 @@ ebookToPDF.includePageNumbers=Add page numbers to the generated PDF
 ebookToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 ebookToPDF.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
 
+#pdfToEpub
+pdfToEpub.title=PDF to EPUB/AZW3
+pdfToEpub.header=PDF to EPUB/AZW3
+pdfToEpub.submit=Convert
+pdfToEpub.selectText=Select PDF file
+pdfToEpub.outputFormat=Output format
+pdfToEpub.outputFormat.epub=EPUB
+pdfToEpub.outputFormat.azw3=AZW3
+pdfToEpub.detectChapters=Detect chapters and insert automatic breaks
+pdfToEpub.targetDevice=Target device
+pdfToEpub.targetDevice.tablet=Tablet / Phone (keeps images high quality)
+pdfToEpub.targetDevice.kindle=Kindle / E-Ink (text-focused, smaller images)
+pdfToEpub.calibreDisabled=Calibre support is disabled. Enable the Calibre tool group or install Calibre to use this feature.
+
 #pdfToCBR
 pdfToCBR.title=PDF 轉 CBR
 pdfToCBR.header=PDF 轉 CBR
@@ -2037,3 +2141,209 @@ pdfToVector.header=PDF to Vector Image
 pdfToVector.description=Convert a PDF into Ghostscript-generated vector formats (EPS, PS, PCL, or XPS).
 pdfToVector.outputFormat=Output format
 pdfToVector.submit=Convert
+
+#####################
+# Exception Hints   #
+#####################
+
+# PDF-related errors
+error.E001.hint.1=Try the 'Repair PDF' feature, then retry this operation.
+error.E001.hint.2=Re-export the PDF from the original application if possible.
+error.E001.hint.3=Avoid transferring the file through tools that modify PDFs (e.g., fax/email converters).
+error.E001.action=Repair the PDF and retry the operation.
+
+error.E002.hint.1=Identify which files are corrupted by processing them one by one.
+error.E002.hint.2=Run 'Repair PDF' on each problematic file before merging.
+error.E002.hint.3=If repair fails, re-export each source document to PDF again.
+error.E002.action=Repair or re-export the corrupted PDFs individually, then retry the operation.
+
+error.E003.hint.1=Use the 'Repair PDF' feature to normalise encryption metadata.
+error.E003.hint.2=If the file uses unusual encryption, re-save with a modern PDF tool.
+error.E003.hint.3=If the PDF is password-protected, provide the correct password first.
+error.E003.action=Repair the PDF or re-export it with compatible encryption.
+
+error.E004.hint.1=PDFs can have two passwords: a user password (opens the document) and an owner password (controls permissions). This operation requires the owner password.
+error.E004.hint.2=If you can open the PDF without a password, it may only have an owner password set. Try submitting the permissions password.
+error.E004.hint.3=Digitally signed PDFs cannot have security removed until the signature is removed.
+error.E004.hint.4=Passwords are case-sensitive. Verify capitalisation, spaces, and special characters.
+error.E063.hint.1=Install FFmpeg on the host system and ensure it is available on the PATH environment variable.
+error.E063.hint.2=Restart Stirling-PDF after installing FFmpeg so the process can detect it.
+error.E063.action=Install FFmpeg and restart Stirling-PDF before retrying the conversion.
+error.E004.hint.5=Some creators use different encryption standards (40-bit, 128-bit, 256-bit AES). Ensure your password matches the encryption used.
+error.E004.hint.6=If you only have the user password, you cannot remove security restrictions. Contact the document owner for the permissions password.
+error.E004.action=Provide the owner/permissions password, not just the document open password.
+
+error.E005.hint.1=Verify the PDF is not empty or contains only unsupported objects.
+error.E005.hint.2=Open the file in a PDF viewer to confirm it has pages.
+error.E005.hint.3=Recreate the PDF ensuring pages are included (not just attachments).
+error.E005.action=Provide a PDF that contains at least one page.
+
+error.E006.hint.1=Ensure the uploaded file is a valid PDF, not another format.
+error.E006.hint.2=If it has a .pdf extension, verify the file is not actually another type (e.g., Word, image).
+error.E006.hint.3=Try opening the file in a PDF reader to confirm validity.
+error.E006.action=Upload a valid PDF file.
+
+# CBR/CBZ errors
+error.E010.hint.1=RAR5 archives are not supported. Repack the archive as RAR4 or convert to CBZ (ZIP).
+error.E010.hint.2=Ensure the archive is not encrypted and contains valid image files.
+error.E010.hint.3=Try extracting the archive with a desktop tool to verify integrity.
+error.E010.action=Convert the archive to CBZ/ZIP or RAR4, then retry.
+
+error.E012.hint.1=Make sure the archive contains image files (e.g., .jpg, .png).
+error.E012.hint.2=Remove unsupported or corrupted files from the archive.
+error.E012.hint.3=Repack the archive ensuring images are at the root or in proper folders.
+error.E012.action=Add at least one valid image to the archive and retry.
+
+error.E014.hint.1=Upload a CBR (RAR) file for this operation.
+error.E014.hint.2=If you have a ZIP/CBZ, use the CBZ conversion instead.
+error.E014.hint.3=Check the file extension and actual format with an archive tool.
+error.E014.action=Provide a valid CBR/RAR file.
+
+error.E015.hint.1=Ensure the ZIP/CBZ is not encrypted and is a valid archive.
+error.E015.hint.2=Verify the archive is not empty and contains image files.
+error.E015.hint.3=Try re-zipping the images using a standard ZIP tool (no compression anomalies).
+error.E015.action=Recreate the CBZ/ZIP without encryption and with valid images, then retry.
+
+error.E016.hint.1=Add images (.jpg, .png, etc.) to the ZIP archive.
+error.E016.hint.2=Remove non-image files or nested archives that aren't supported.
+error.E016.hint.3=Ensure images are not corrupted and can be opened locally.
+error.E016.action=Include at least one valid image in the CBZ file.
+
+error.E018.hint.1=Upload a CBZ (ZIP) file for this operation.
+error.E018.hint.2=If you have a RAR/CBR, use the CBR conversion instead.
+error.E018.hint.3=Check the file extension and actual format with an archive tool.
+error.E018.action=Provide a valid CBZ/ZIP file.
+
+# EML errors
+error.E020.hint.1=Verify the uploaded file is not zero bytes.
+error.E020.hint.2=Export the EML again from your email client.
+error.E020.hint.3=Ensure the file hasn't been stripped of content by email/security tools.
+error.E020.action=Upload a non-empty EML file.
+
+error.E021.hint.1=Ensure the file is a raw EML message, not MSG or another email format.
+error.E021.hint.2=Re-export the email as EML from your client.
+error.E021.hint.3=Open the file with a text editor to verify standard EML headers are present.
+error.E021.action=Provide a valid EML file export.
+
+# File processing errors
+error.E030.hint.1=Confirm the file ID or path is correct.
+error.E030.hint.2=Ensure the file wasn't deleted or moved.
+error.E030.hint.3=If using a temporary upload, re-upload the file and try again.
+error.E030.action=Provide an existing file reference and retry.
+
+error.E031.hint.1=Check that the file is not corrupted and is supported by this operation.
+error.E031.hint.2=Retry the operation; transient I/O issues can occur.
+error.E031.hint.3=If the problem persists, simplify the document (fewer pages, smaller images).
+error.E031.action=Verify the file and operation parameters, then retry.
+
+error.E032.hint.1=Attach a file in the request.
+error.E032.hint.2=Make sure the file is not zero bytes.
+error.E032.hint.3=If uploading multiple files, ensure at least one is provided.
+error.E032.action=Upload a non-empty file and retry.
+
+error.E033.hint.1=Provide a filename with an extension.
+error.E033.hint.2=Ensure your client includes the original filename during upload.
+error.E033.action=Include a filename for the uploaded file.
+
+error.E034.hint.1=Verify the image file is not corrupted and can be opened locally.
+error.E034.hint.2=Ensure the file format is a supported image type.
+error.E034.hint.3=Re-export or convert the image to a standard format (JPEG/PNG).
+error.E034.action=Provide a readable, supported image file.
+
+# OCR errors
+error.E040.hint.1=Select at least one OCR language from the options.
+error.E040.hint.2=If unsure, choose the primary language of the document's text.
+error.E040.hint.3=Multiple languages can be selected if mixed text is present.
+error.E040.action=Specify one or more OCR languages.
+
+error.E041.hint.1=Use valid language codes (e.g., eng, fra, deu).
+error.E041.hint.2=Remove unsupported or misspelt language codes.
+error.E041.hint.3=Check installed OCR language packs and install missing ones.
+error.E041.action=Provide valid OCR language codes or install missing language packs.
+
+error.E042.hint.1=Install OCR tools (e.g., OCRmyPDF/Tesseract) as per documentation.
+error.E042.hint.2=Verify the tools are on the PATH and accessible by the application.
+error.E042.hint.3=If running in Docker, use an image variant that includes OCR tools.
+error.E042.action=Install and configure the OCR tools.
+
+error.E043.hint.1=Use 'hocr' for HTML OCR output or 'sandwich' to embed text in PDF.
+error.E043.hint.2=Check the API docs for valid render types.
+error.E043.hint.3=Avoid typos; values are case-sensitive.
+error.E043.action=Choose either 'hocr' or 'sandwich' as render type.
+
+error.E044.hint.1=Check the server logs for the detailed OCRmyPDF error output.
+error.E044.hint.2=Ensure required OCR dependencies and language packs are installed.
+error.E044.hint.3=Try running OCR locally on the file to reproduce the issue.
+error.E044.action=Investigate OCR logs and fix missing dependencies or inputs, then retry.
+
+# Compression/processing errors
+error.E050.hint.1=Provide both target output size and optimisation level.
+error.E050.hint.2=Review API docs for required compression parameters.
+error.E050.hint.3=If unsure, start with default optimisation and adjust.
+error.E050.action=Specify expected output size and optimise level for compression.
+
+error.E051.hint.1=Confirm Ghostscript is installed and accessible.
+error.E051.hint.2=Simplify the PDF (e.g., reduce image sizes) and retry.
+error.E051.hint.3=Review command-line arguments generated for Ghostscript in logs.
+error.E051.action=Ensure Ghostscript is installed and the command executes successfully.
+error.E054.hint.1=Convert EPS or PS files to a single-page PDF before retrying this operation.
+error.E054.hint.2=Export each page individually from the authoring application so Ghostscript processes a single page at a time.
+error.E054.hint.3=Use the Convert to PDF tool to flatten artwork or advanced effects, then rerun the command.
+error.E054.action=Convert the source file to a single-page document (or PDF) and retry the operation.
+
+error.E052.hint.1=Ensure qpdf is installed and on PATH.
+error.E052.hint.2=Verify that the PDF is not corrupted before compression.
+error.E052.hint.3=Adjust compression parameters if the command fails.
+error.E052.action=Install qpdf and retry with valid inputs.
+
+error.E053.hint.1=The operation was cancelled or interrupted by the system.
+error.E053.hint.2=Avoid terminating the process or closing the browser mid-operation.
+error.E053.hint.3=Retry the operation; if it persists, check server resource limits.
+error.E053.action=Retry the operation and avoid interruption.
+
+# Conversion/System errors
+error.E060.hint.1=Ensure the PDF is valid and supported by the converter.
+error.E060.hint.2=Try converting to a different PDF/A level or re-export the source to PDF first.
+error.E060.hint.3=Remove problematic elements (e.g., complex transparency) and retry.
+error.E060.action=Adjust conversion settings or normalise the PDF, then retry.
+
+error.E061.hint.1=Provide either a single HTML file or a ZIP containing HTML and assets.
+error.E061.hint.2=Ensure relative links in HTML point to included assets in the ZIP.
+error.E061.action=Upload an HTML file or a ZIP of the website content.
+
+error.E062.hint.1=Install Python and required WebP libraries to enable conversion.
+error.E062.hint.2=If using Docker, use an image variant with Python/WebP support.
+error.E062.hint.3=Check PATH and environment to ensure Python is available.
+error.E062.action=Install Python and WebP dependencies.
+
+# Validation errors
+error.E070.hint.1=Review the parameter's allowed values in the API docs.
+error.E070.hint.2=Ensure the value format matches expectations (case, range, pattern).
+error.E070.hint.3=Correct the argument and resend the request.
+error.E070.action=Provide a valid parameter value and retry.
+
+error.E071.hint.1=Include the missing parameter in the request.
+error.E071.hint.2=Verify your client sends all required fields.
+error.E071.action=Add the required parameter and retry.
+
+error.E072.hint.1=Use formats like 'A4', 'Letter', or 'WIDTHxHEIGHT' (e.g., 800x600).
+error.E072.hint.2=Ensure units and separators are correct.
+error.E072.hint.3=Refer to docs for supported sizes.
+error.E072.action=Provide a supported page size value.
+
+error.E073.hint.1=Allowed values: 'greater', 'equal', 'less'.
+error.E073.hint.2=Check for typos and use lowercase.
+error.E073.hint.3=Consult API docs for comparator usage examples.
+error.E073.action=Use one of 'greater', 'equal', or 'less' as comparator.
+
+# System errors
+error.E080.hint.1=Your Java runtime may not include MD5. Use an alternative algorithm.
+error.E080.hint.2=If hashing is optional, switch to SHA-256 or another supported digest.
+error.E080.hint.3=Install appropriate security providers if MD5 is required.
+error.E080.action=Use a supported hash algorithm (e.g., SHA-256) or install MD5 provider.
+
+error.E081.hint.1=Reduce the DPI (try 150 or lower).
+error.E081.hint.2=Process the document in smaller chunks or fewer pages at a time.
+error.E081.hint.3=Reduce page dimensions or image complexity before rendering.
+error.E081.hint.4=Increase available heap memory for the application if possible.
+error.E081.action=Lower the DPI and retry; 150 DPI is recommended for large pages.