[Comments] PDF document authors can provide an explanation for abbreviations either by providing the expanded form immediately following the first instance of the abbreviation, by linking to a definition of the abbreviation, or by providing expansion text as a text equivalent to the abbreviation text. PDF supports abbreviations in tagged PDF by using a span and an abbreviation property. The ISO 32000-1 PDF Specification details abbreviation support in section 14.9.5. Test results: Test id 18 (Markup abbreviations in PDF tags) [Checkpoint] 
3.1.4 Abbreviations: A mechanism for identifying the expanded form or meaning of abbreviations is available. (Level AAA)