This section describes the standard tag types that apply to tagged PDFs. These standard tags provide assistive software and devices with a base set of semantic and structural elements to use in interpreting document structure and presenting content to a user in a useful manner.
The PDF tags architecture is extensible, so any PDF document can contain any tag set that an authoring application decides to use. For instance, a PDF might have XML tags that came in from an XML schema. Any custom tags that you define (such as tag names that were generated from paragraph styles from an authoring application) should have a role map that matches each custom tag to one of the standard tags here. When assistive software encounters a custom tag, the software can refer to this role map and properly interpret the tags. Tagging PDFs by using one of the methods described in this guide generally produces a correct role map for the document.
The standard Adobe element tag types are available in the New Tag dialog box and in the TouchUp Properties dialog box in Acrobat Professional or Acrobat 3D. Adobe strongly encourages using these tag types, because they provide the best results when tagged content must be converted to a different format, such as HTML, Microsoft Word, or an accessible text format for use by other types of assistive technology.
Block-level elements are page elements that consist of text laid out in paragraph-like forms. Block-level elements are part of a document’s logical structure. Such elements are further classified as container elements, heading and paragraph elements, label and list elements, special text elements, and table elements.
Container elementsContainer elements are the highest level of element and provide hierarchical grouping for other block-level elements.
Heading and paragraph elementsHeading and paragraph elements are paragraph-like, block-level elements that include specific level heading and generic paragraph (P ) tags. A heading (H) element should appear as the first child of any higher-level division. Six levels of headings (H1 to H6) are available for applications that don’t hierarchically nest sections.
Label and list elementsLabel and list elements are block-level elements used for structuring lists.
Special text elementsSpecial text elements identify text that isn’t used as a generic paragraph (P).
Table elementsTable elements are special elements for structuring tables.
Inline-level elementsInline-level elements identify a span of text that has specific formatting or behavior. They are differentiated from block-level elements. Inline-level elements may be contained in or contain block-level elements.
Special inline-level elementsSimilar to inline-level elements, special inline-level elements describe an inline portion of text that has special formatting or behavior.