Provide expansions for abbreviations in PDFs
A PDF tag can carry an E entry that attaches an expansion to an abbreviation, so a Span reading "SEC" exposes "Securities and Exchange Commission" to assistive technology. The E entry works on any structure element, not only a Span, so a column header tagged TH can carry one too. W3C publishes PDF8 as a sufficient technique, paired with the requirement to spell the term out on its first use in the text. The rule it answers is a level AAA one, so we report this as a strong improvement in dense legal and financial documents rather than a hard failure, and the expansion in the text matters as much as the one in the tag tree.
How we find it in an audit
We read the document with a screen reader and note abbreviations that are never expanded anywhere. Not in the text, not in a glossary, not in the tags. In Acrobat's Tags panel we check abbreviation spans for E entries through the tag properties. We raise this mainly in legal and financial documents, where the shorthand carries the meaning and a first-time reader has no way to decode it.
How affected users experience it
The reader hears "Pursuant to RESPA and TILA" spelled letter by letter, or mangled into a pseudo-word, with no way to look it up in context. Sighted readers can at least skim back for a first spelled-out use. A screen reader user cannot skim a PDF that offers no structure to skim by.
Passes vs. fails
Passes
First occurrences are expanded in the text itself, "Truth in Lending Act (TILA)", and the tagged abbreviation spans carry E entries with the expansion for assistive technology.
Fails
A mortgage disclosure uses "TILA", "RESPA" and "APR" throughout and never spells any of them out. Screen readers spell the letters, and the meaning is never given.
Other ways to satisfy this rule
7 guides on this site are filed under 3.1.4 Abbreviations. W3C lists this one as sufficient for that rule only alongside G102, so the pair is what passes and neither half does on its own.
- G55sufficientLink unusual words to their definitions
- G62sufficientProvide a glossary for specialized terms
- G70sufficientOffer a dictionary search for specialized content
- G97sufficientExpand each abbreviation at its first use
- G102sufficientExplain every abbreviation where it first appears
- H28advisoryExplain abbreviations with the abbr element
This guide is our interpretation of W3C technique PDF8: Providing definitions for abbreviations via an E entry for a structure element. W3C publishes its techniques as guidance rather than as the standard, and says so on every one of them. The success criterion is what conformance is measured against, and a technique is one documented way to meet it.