PDF/UA

PDF/UA (ISO 14289, where UA stands for Universal Accessibility) is the standard that makes a PDF usable by people who rely on assistive technology. A screen reader cannot make sense of ink on a page; it needs a logical structure underneath. PDF/UA defines exactly how that structure must be built.

The core requirement is a tagged document: headings, paragraphs, lists, tables and figures are marked up as semantic elements in a tag tree, and that tree fixes the reading order independently of where the text physically sits on the page. Images carry alternative text, tables expose their row and column headers, and the document's language is declared so a screen reader pronounces it correctly. None of this changes how the page looks; it adds a parallel layer of meaning.

A properly tagged PDF/UA file is also easier to convert, search and reflow, which helps everyone, not only assistive-technology users. Because the structure is part of the file, an accessible document stays accessible wherever it travels, with nothing to re-process on a remote service.