What's the difference between PDF/UA and WCAG?
Updated
WCAG is the general web-content accessibility standard (perceivable, operable, understandable, robust); PDF/UA (ISO 14289) is the PDF-specific technical standard defining exactly how a compliant PDF must be built — tags, reading order, metadata, artifacts. In practice they overlap heavily: a properly tagged PDF/UA document satisfies the document-relevant WCAG criteria, and regulations (508, EAA/EN 301 549) reference WCAG while auditors test PDFs with PDF/UA checks.
Think of WCAG as the law's language and PDF/UA as the engineering spec: WCAG says 'content must have a meaningful sequence'; PDF/UA says precisely which structures inside a PDF encode that sequence.
Automated PDF checkers (PAC, veraPDF, and this site's audit) test the PDF/UA machine-checkable layer — the concrete, testable requirements — and report WCAG mappings alongside.
For compliance purposes you rarely choose between them: regulations cite WCAG; your PDF passes by being built to PDF/UA practice.