diff --git a/tests/resources/README.rst b/tests/resources/README.rst
index afa1ce19..c495ebdf 100644
--- a/tests/resources/README.rst
+++ b/tests/resources/README.rst
@@ -57,7 +57,7 @@ under the terms of the license in LICENSE.rst.
         - test image with 200 x 100 DPI resolution
     *   - blank.pdf
         - @jbarlow83
-        - blank PDF
+        - blank PDF generated by Adobe Illustrator CC 17, containing a lot of application-specific metadata/bloat
     *   - cmyk.pdf
         - @jbarlow83
         - a CMYK image created in Photoshop