The Web Content Accessibility Guidelines (WCAG) 2.1 AA and the PDF/UA (ISO 14289-1) standard both serve the overarching goal of making digital information accessible, but they were created for different purposes, apply in different contexts, and provide different levels of specificity for PDF documents. WCAG 2.1 AA is a set of success criteria focused on accessibility for all digital content and user interfaces on the web. In contrast, PDF/UA is a technical standard dedicated exclusively to the structure, tagging, and user experience requirements of PDF documents. As a result, both standards overlap conceptually, but PDF/UA adds important rules that WCAG alone does not define.
Both WCAG 2.1 AA and PDF/UA share the same functional foundation: ensuring that users with disabilities can perceive, understand, navigate, and interact with content effectively. Many WCAG principles such as text alternatives for images, sufficient color contrast, keyboard accessibility, logical reading order, and descriptive link text directly apply to PDFs and are echoed within PDF/UA. Both standards also emphasize semantic structure (such as headings, lists, and tables) and the importance of accessibility for assistive technology users, including screen reader compatibility.
Because of this alignment, meeting WCAG 2.1 AA can significantly improve the accessibility of a PDF. Many accessibility checklists, especially at universities, government agencies, and public institutions, pair WCAG and PDF/UA requirements together when evaluating document accessibility.
However, the differences between the two standards are substantial. WCAG 2.1 AA is outcome-based: it defines what users need to be able to do but rarely prescribes how content should be technically implemented. It is also not PDF-specific; WCAG applies to HTML, apps, media players, widgets, and any other web-delivered content.
PDF/UA, on the other hand, is prescriptive and format specific. It provides explicit rules for how a PDF must be authored internally. For example, PDF/UA requires:
WCAG does not provide these detailed PDF technical requirements. A PDF can meet WCAG success criteria in theory while still failing PDF/UA because its tagging structure, role maps, or DOM order are not technically valid according to the ISO standard.
The highest level of PDF accessibility is achieved when both standards are applied together, but PDF/UA is the more definitive and comprehensive standard for PDF-specific accessibility. WCAG 2.1 AA ensures that the content within the PDF meets essential accessibility requirements, while PDF/UA ensures that the file format itself is properly engineered for assistive technologies.
If an organization must choose only one standard to evaluate the technical accessibility of PDFs, PDF/UA provides the more complete and rigorous requirements. However, WCAG 2.1 AA remains essential because many legal frameworks—such as Section 508 and the Americans with Disabilities Act Title II—reference WCAG rather than PDF/UA. In practice, a PDF that meets PDF/UA will typically satisfy most WCAG success criteria relevant to documents, but not necessarily the other way around.
WCAG 2.1 AA and PDF/UA are complementary rather than competing standards. WCAG establishes broad accessibility expectations for content and user experience, while PDF/UA provides precise technical requirements to ensure that PDFs function correctly with assistive technology. PDFs that meet both standards are significantly more accessible, robust, and compliant than those evaluated against WCAG alone.