PDF/UA-1 · CLAUSE 7.21.7
Characters cannot be mapped to Unicode
The font does not define a usable mapping from character codes to Unicode values, or the ToUnicode CMap contains invalid values.
Why it matters
Screen readers and copy-paste produce gibberish because the reader cannot tell which actual characters the glyphs represent. Visually the page looks perfect, which makes this failure easy to miss.
How to fix it
- Embed fonts with a valid ToUnicode CMap.
- Replace symbol or icon fonts used for text with real text plus proper alt descriptions.
- Verify by copying text out of the PDF: if the pasted text is wrong, this rule is why.
WCAG 1.3.1 Info and Relationships (A)
What the standard says
The Unicode values specified in the ToUnicode CMap shall all be greater than zero (0), but not equal to either U+FEFF or U+FFFE
Check your own PDF
Validate a file against PDF/UA-1 and see whether this rule fails in your document.
curl -sS -X POST "https://api.ua1.dev/api/validate?format=compact&profile=ua1" \ -F "file=@document.pdf"