Definition
PDF/UA
ISO 14289 — the technical standard for universally accessible PDFs: complete tagging, correct reading order, metadata, artifact marking, embedded fonts. The spec auditors' machine checks are built on.
Where WCAG states outcomes, PDF/UA states construction: exactly which structures a conforming file contains. The Matterhorn Protocol enumerates its checkpoints — split between machine-checkable (what automated tools verify) and human-judgment items.
Related tools & guides
Authoritative sources: iso.org
Check whether your PDF is accessible
Ceereo audits any born-digital PDF against PDF/UA and WCAG machine checks for free, then writes the missing accessibility layer into the same file. The document looks exactly the same afterwards.