Accessible PDFs are also known as “tagged” PDFs. They contain a hidden network of instructions and provide a textual representation of the document so that people using screen readers can properly navigate the document.
Properly tagged PDFs also benefit from better search engine optimization (SEO) because search engines read the words between header tags before anything else.
There are countless programs that enable you to save a document as a PDF. Not all of those programs, however, will produce tagged PDF files. There is also more to making an PDF accessible than simply adding tags.
Anatomy of an Accessible PDF
These criteria represent the basic features of an accessible PDF (source: Adobe).
1. Hierarchical Heading Structure and Logical Reading Order
The sections of your PDF must be organized so that screen readers know the difference between different sections (titles, section headers, subsection headers, and text body) and content like tables and sidebars.