What are PDF tags?

Tags are the basis for accessibility within a PDF. Without proper tags there is no accessibility. Tag elements provide semantic information for screen readers, control the reading order, and other important functions. An important first step is to determine if your PDF has tags. Review this post to find out if your document has tags.

Why do PDF tags matter?

Assistive technology will read tags and use them as a method for navigating larger documents. A tagged PDF is essential for those with visual disabilities and anyone who is using assistive technology like JAWS or NVDA.

PDF tags make it possible to identify content like headings, lists, links, tables, forms, and other important features. Not all programs can export a tagged PDF – so make sure you are using the right tools!

Sample screenshot of tags panel

Video overview of PDF Tags

Tag Relationships

Tags come in a pair and can sometimes be referred to as a Parent-Child relationships. In the example below the Figure tag is the parent tag and image container is the Child tag.

Every parent tag will have a child tag. This is useful for moving tags around in the tags panel.

The PDF Tags breakdown

If a tag is not properly categorized it will fail accessibility checks and be confusing to its users. Adding tags does not change the visual appearance of the document; it provides invisible layer of formatting within the document that works with screen readers. PDF tags also allows the content to reflow seamlessly on devices with smaller screens, like smartphones and tablets. Here is a brief explanation of what each tag represents:

<P>

The P tag is the most basic and universal tag. This tag is used as body text.

<H1> <H2> <H3> <H4> <H5> <H6>

These are heading tags. Most documents will have a single H1 tag, but larger documents could contain more. Modern assistive technology can recognize up to six heaving levels. Always use headings in order. Think of them like an outline.

1. The Parent Tag <H1>
2. The child tag (container)
3. The content the tag is referencing (content on page)

<L> <LI> <Lbl> <LBody>

List elements contain a specific structure. These tags represent the structure of accessible lists. Some accessibility guidelines require the use of Lbl and other guidelines do not.

1. List Parent Tag <L>
2. List Item Child Tag <LI>
3. Label <Lbl>
4. List Body child Tag <LBody>
5. Contents of First list item
6. List item content on page

<Figure>

The figure tag represents any and all images. At this time the figure tag is used for all graphics within a PDF.

1. <Figure> is a parent tag
2. The Image is a child tag (container)
3. The image as content on page

<Table> <TR> <TH> <TD>

Reading plain text is an easy task for assistive technologies. A table of data presents a complex more task. Proper PDF tag structure makes this possible by identifying essential information including the number of rows and columns as well as column (or row) headers, and which heading each data entry corresponds to. The more complex a table is, the more significant the challenge to tag it correctly.

1. Table Parent Tag <Table>
2. Table Row Child tag <TR>
3. Table Header Cell <TH>
4. Table Data Cell <TD>
5. Table on Page

<Link>, Link – OBJR

Every link tag needs a Link-OBJR tag.

1. Parent tag <P>
2. Link Tag <Link>
3. Link Reference Object
4. The link Text on screen
5. Content on page

<Reference> & <Note>

Reference and Note tags are up for interpretation but are commonly used within PDFs to “visually” break content apart.

Reading Order

An accessible PDF provides the instructions to the assistive technologies such as screen readers to read the content properly and in the correct order. The tag order within the tag tree will determine the reading order of the document. For documents without this logical structure, the best case would be that assistive technologies would guess at the correct order that the content should be presented in. In worst cases, the content would be completely unable to be read. The outcome is that the content becomes useless to the user.

How do I apply tags to a document?

There are multiple methods to apply tags to a document. The most common methods are:

• Word to PDF Conversion
• The make accessible action wizard
• Auto tagging
• Manually tagging

Advanced Tag Breakdown

The following is a detailed breakdown of available tag structure within a pdf. It has been adapted from https://accessible-pdf.info/basics/general/overview-of-the-pdf-tags

Grouping elements

PDF tag	Semantic meaning	Possible and semantically meaningful parent elements	Possible and semantically meaningful child elements
Document	Represents a complete document	–	Grouping elements, Block-level structure elements
Part	Division of a larger document into smaller, associated parts	Document	Art, Sect, Div, BlockQuote, Caption, TOC, Index,
Art	Parts of content which together are conclusive, i.e. an article or part of a document	Document, Part, Sect, Div, BlockQuote	Sect, Div, BlockQuote, Caption, TOC, Index,
Sect	Grouped related content parts, for example several paragraphs, which can be combined into a group	Document, Part, Art, Sect, Div, BlockQuote	Art, Sect, Div, BlockQuote, Caption, TOC, Index,
Div	Generic group element without semantic meaning	Document, Part, Art, Sect, Div, BlockQuote	Art, Sect, Div, BlockQuote, Caption, TOC, Index,
BlockQuote	One or more paragraphs that originate from another author, in other words, that have been quoted	Document, Part, Art, Sect, Div	Art, Sect, Div, Caption,
Caption	A caption to describe for example a picture or a table	Document, Part, Art, Sect, Div, BlockQuote, Table, L	Sect, Div, BlockQuote,
TOC	Container for table of contents entries. Can be used either as a flat hierarchy (all contained TOCI on one level) or as a complex hierarchy (TOC within a TOCI as a subgroup). Can be contained multiple times in a document, since it can also be used for image or table directories.	Document, Part, Art, Sect, Div	TOCI
TOCI	Entry within a table of contents (TOC).	TOC	TOC, P, Lbl, Reference
Index	Container for a subject index	Document, Part, Art, Sect, Div	L

Block-level structure elements

Paragraph elements

PDF tag	Semantic meaning	Possible and semantically meaningful parent elements	Possible and semantically meaningful child elements
P	Ordinary paragraph	Document, Part, Art, Sect, Div, BlockQuote, Caption, TOCI	Inline-level structure elements
H1, H2, H3, H4, H5, H6	Hierarchical headings on levels 1 to 6	Document, Part, Art, Sect, Div, BlockQuote	Inline-level structure elements

List elements

PDF tag	Semantic meaning	Possible and semantically meaningful parent elements	Possible and semantically meaningful child elements
L	List container; groups together all list elements that belong together	Document, Part, Art, Sect, Div, BlockQuote, Index	LI, Caption
LI	Container of a list entry; can contain an L to create multi-level lists	L	Lbl, LBody, L
Lbl	Comes from the term “label” and represents the numbering or bullet character within a list. It’s not actually a block-level structure element and can also be used in other elements such as TOCI or Caption.	LI	–
LBody	Contains the contents of a list entry	LI	Inline-level structure elements

Table elements

PDF tag	Semantic meaning	Possible and semantically meaningful parent elements	Possible and semantically meaningful child elements
Table	Table container; combines all related table elements	Document, Part, Art, Sect, Div, BlockQuote	TR, Caption, THead, TBody, TFoot
TR	Groups a table row	Table, THead, TBody, TFoot	TH, TD
TH	Table heading cell; describes the meaning either at horizontal (line) or vertical (column) level	TR	Inline-level structure elements
TD	Ordinary table data cells	TR	Inline-level structure elements
THead	A group of table rows (TR) to mark them as table header; can be used optionally	Table	TR
TBody	A group of table rows (TR) to mark them as table content; can be used optionally	Table	TR
TFoot	A group of table rows (TR) to mark them as table footer; can be used optionally	Table	TR

Inline-level structure elements

PDF tag	Semantic meaning	Possible and semantically meaningful parent elements	Possible and semantically meaningful child elements
Span	Generic container without semantic meaning; is used, among other things, for visual markups, language changes or for adding ActualText (e.g. for ignoring hyphens)	P, H1–H6, LBody, TD, Quote, Note	–
Quote	Used like BlockQuote for quoted content; however, Quote is used at line level	P, H1–H6, LBody, TD	Span
Note	Footnote or endnote text (not the reference character in the body text). The footer/end-note character within Note and Reference will be placed in a Lbl.	P, H1–H6, LBody, TD	Lbl, P, Span
Reference	Refers to another place in the document, e.g. footnote or directory entry	P, H1–H6, LBody, TD	Lbl
Code	Marking of programming language	P, H1–H6, LBody, TD	–
Link	Link to a web page or to a place within the document	P, H1–H6, LBody, TD	–
Annot	Annotations that are not a link or a widget (form field), like comments and videos.	P, H1–H6, LBody, TD	–

Illustration graphic elements

PDF tag	Semantic meaning	Possible and semantically meaningful parent elements	Possible and semantically meaningful child elements
Figure	Photo or graphic	Document, Part, Art, Sect, Div, BlockQuote, P, LBody, TD	–
Formula	Mathematical formula	Document, Part, Art, Sect, Div, BlockQuote, P, H1–H6, LBody, TD	–
Form	Form element	Document, Part, Art, Sect, Div, P, TD	–

How to add tags to a PDF

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