Tagged PDF
A tagged PDF contains a hidden layer of structure - tags - that tells what each piece of content is and in what order to read it: this is a level-two heading, this is a list of four items, this table cell belongs to that column header, this image means X, this flourish is decorative and should be skipped.
Without tags, a PDF is just ink positioned on a page: a has to guess what's a heading, where paragraphs begin, and what columns should be read in - and often guesses wrong. Tags are invisible to sighted readers and don't change the document's appearance at all. Content that a tag doesn't cover should be marked as an instead, so nothing is left ambiguous.
Most accessibility failures in PDFs come down to missing, incomplete, or incorrect tags. Rebuilding this structure correctly is the core of what PDF remediation does. These structure tags are not the same as you apply to documents for grouping.
Learn more
- Tagged PDF Best Practice Guide: Syntax - the PDF Association's developer's guide to tagged PDF