PAC (PDF Accessibility Checker)

PAC (PDF Accessibility Checker) at a glance

PAC (PDF Accessibility Checker) is a free validation tool provided by axes4 GmbH for testing the accessibility of PDF documents. It is widely regarded as a de-facto standard validator for PDF/UA (ISO 14289-1) and additionally covers numerous WCAG success criteria through automated and semi-automated checks. It is commonly used by government agencies, educational institutions, and organizations that must meet legal digital accessibility requirements as part of document release or quality-assurance workflows.

The tool is released in named yearly editions that, at irregular intervals, introduce new test rules, a revised rule set, or additional functionality such as AI-assisted support for manual review steps. Between major editions, occasional bug fixes and minor adjustments to the checking logic are published.

For administrators it is relevant that PAC is distributed as a Windows application (sometimes run via Wine on macOS/Linux) and has no automatic update mechanism comparable to a package manager; new versions must be downloaded manually from the vendor's website. When moving to a new yearly edition, changes to the rule set should be reviewed, since PDFs previously classified as compliant may be re-evaluated differently after a rule-set update.