Test PDF accessibility (PDF/UA conformance) - tagged-PDF structure (StructTreeRoot), alternative text on images (Alt), reading-order, language metadata (Lang), document title, heading hierarchy. Use veraPDF / PAC (PDF Accessibility Checker) / pdfix / Adobe Acrobat Pro headless; map each finding back to WCAG 2.1 PDF Techniques (PDF1 - PDF23). Use when a product ships customer-facing PDFs into a context that mandates PDF/UA - US Section 508, EU Directive 2016/2102, or a public-sector tender - and each file must be proven tagged before release.