Logical reading order must be verified manually in PDFs. Verify the reading order displayed in the Tags panel to make sure it matches the logical reading order of the document and make adjustments as necessary.
To check reading order:
Visit Reading Order tool overview for more information.
Many PDFs require a manual check of color contrast to ensure they are accessible to people who are color blind or have low vision.
Text color should be easily viewable and should not be the only indicator of meaning or function. Color balance should have at least a 4.5:1 ratio for small text and 3:1 ratio for large text.
Color contrast is important because text and background colors can determine how people interact with the content that is written in those colors. Low-contrast colors are difficult to read when text contrasts poorly with background colors, while high-contrast colors are easier to read when paired together.
When in doubt, these color combinations provide high contrast:
Use the Colour Contrast Analyser, a free app that analyzes colors and contrast, and displays results almost immediately, to check color contrast.
Alternatively, you can apply high-contrast colors to the PDF.
If a PDF is a scanned file, it is likely completely inaccessible to some users. Scanned files are often images, so if text is included, a screen reader has no way to discern the text. Instead of a scanned or image-only file, an accessible version must be provided.