Many PDF tags are functionally identical to HTML tags for accessibility purposes.
“Semantically appropriate tags” refers to the choice of structure element type (tag type) used to represent the document’s semantic structure, including section and subsection heading, paragraph, list, table, figure, and other elements. The term “semantically appropriate” implies that the tags are so chosen as to accurately represent the author’s intent. (Paraphrased from the AIIM website.)
Once reading order is checked and verified, the next step is to ensure tag types are appropriate for the content they contain.
Once you have a good sense of how the process of correcting reading order goes you’ll find it easy to verify and correct both the reading order and ensure appropriate tags (semantics) at the same time.
“Semantics” in the PDF context refers to the purpose of each block of text as established by its tag. For example, headings (<H1>, <H2>, etc.) are used for text that organizes other text contained in paragraph (<P>) tags.
To ensure PDF tags have appropriate semantics the following types of information must be exposed to assistive technologies by the appropriate selection of tag type or attribute:
The language of content must be indicated. See CommonLook PDF’s language management facility.
Expansion Text (Acronyms and Abbreviations)
Acronyms and abbreviations often confuse the voicing systems in assistive technology. CommonLook PDF helps manage the AT experience of acronyms and abbreviations through PDF’s expansion text capability.
The longer and more complex the document, the more important a valid heading structure is for effective navigation with a screen reader. Learn more about Headings.
Graphics used to convey information require an alternative text description. Learn more about how to use alt text and actual text.