What are PDF Tags?  

PDF tags are hidden markers that define the logical structure and reading order of content within a PDF document. They work like HTML tags, identifying different elements like headings, paragraphs, and lists. Think of them as labels that tell assistive technologies what type of content they're encountering. 

Why are Tags Important? 

Tags serve several crucial purposes:

• Make PDFs accessible to screen readers and other assistive technologies
• Enable proper content flow on mobile devices
• Preserve document structure when converting to other formats
• Helps to maintain a logical reading order
• Supports compliance with accessibility standards (Section 508 and WCAG 2.2)  

Tag Tree 

A document's invisible tags form a hierarchical structure called a tag tree. It shows how content elements in a PDF relate to each other. It's similar to an HTML DOM tree, where elements are nested within other elements. The tag tree determines: 

• The logical reading order of the document
• Parent-child relationships between elements
• The structural organization of content 

While the tag tree is designed to reflect the document's structure, it is essential to review and verify its accuracy to ensure proper tagging. Any content missing from the tag tree will likely be inaccessible to screen readers. 

Common PDF Tags 

These are the most frequently used PDF tags:
Document Structure: 

• <Document> - Root element
• <Part> - Major document sections
• <Sect> - Subsections 

Text Elements: 

• <H1> to <H6> - Heading levels
• <P> - Paragraphs
• <L> - Lists
• <LI> - List items 

Tables: 

• <Table> - Table container
• <TR> - Table rows
• <TH> - Table headers 
• <TD> - Table cells 

Summary 

PDF tagging is a fundamental step when creating accessible documents. By properly applying tags, you ensure your PDFs are usable by everyone, including those who rely on assistive technologies. Remember that tagging is not just about compliance—it's about creating inclusive content that can be accessed, understood, and used by all readers. Start with the basic tags listed above, and gradually incorporate more complex tagging as you become comfortable with the process. 

Resources 

• Adobe Acrobat Pro help with the tagging panel, step-by-step instructions Edit document structure with the Content and Tags panel. 
• Adobe Accessibility Resource Center - Create and verify PDF Accessibility 
• More learn more/how to’s at How to Make Materials Accessible
• Section 508 PDF Guide - Create Accessible PDFs 
• Section08.gov series of videos to explain and demonstrate PDF accessibility in How to Test and Remediate PDFs for Accessibility Using Adobe Acrobat. 
• WebAIM Defining PDF Accessibility - PDF Accessibility