A tagged PDF includes a hidden structure layer that helps screen readers and other assistive technology understand and navigate the document.
Tags do not change how the PDF looks. Your visual layout, branding, fonts, colors, and images remain the same. Instead, PDF tags add information behind the visible page to support a meaningful reading experience for assistive technology users.
What a tagged PDF is
A tagged PDF uses structural labels, known as PDF tags, to describe the purpose and relationship of document content. This structure supports document accessibility by helping assistive technology identify headings, paragraphs, lists, tables, links, images, and form fields.
Think of tags as the document’s underlying map. They tell a screen reader where a heading begins, which items belong in a list, how a table is organized, and what order to read the content.
Common PDF tags include:
- Headings to identify section titles and establish hierarchy
- Paragraphs to distinguish regular body text
- Lists to group related items in the correct sequence
- Tables to connect headers and data cells
- Links to identify linked text and its destination
- Figures to provide alternative text for meaningful images
A properly tagged PDF also has a logical reading order. This means a screen reader should present the content in the same meaningful sequence intended by the document author.
Tagged vs. untagged PDFs
A tagged PDF and an untagged PDF may look identical on screen. The difference becomes clear when someone uses a screen reader, keyboard navigation, or another assistive technology.
In a tagged PDF, the software can identify the document title, move between headings, announce list items, and communicate the relationship between table headers and data. A user can navigate the document more efficiently and understand how the content is organized.
In an untagged PDF, content may be read in the wrong order or as one long block of text. A screen reader may not recognize headings, tables, or images correctly. For example, it could read a page footer in the middle of a paragraph or announce separate table cells without explaining their relationship.
| Tagged PDF | Untagged PDF |
|---|---|
| Provides a structure layer for assistive technology | Provides little or no usable structure |
| Supports logical reading order | May be read in an illogical sequence |
| Identifies headings, lists, tables, and links | May present content as disconnected text |
| Enables more efficient navigation | Makes navigation more difficult |
| Keeps the visible design unchanged | Can look visually correct but remain difficult to use |
Tags are not visible to most readers, but they make a substantial difference to how people experience a document.
Why PDF tags matter for accessibility
PDF tags help ensure that information is available to people who cannot rely on visual formatting alone. They support users who navigate documents with a screen reader, keyboard, refreshable braille display, or other assistive technology.
For example, a visually formatted heading may use a larger font and bold styling. Without a heading tag, however, a screen reader cannot reliably tell the user that the text begins a new section. Similarly, a visual table may appear clear to a sighted reader but be confusing if its cells are not tagged correctly.
Tags are an important foundation for digital accessibility, but they are not enough on their own. A document also needs meaningful alternative text, accurate reading order, clear link text, correctly structured tables, and usable form fields.
Tags support standards such as PDF/UA, which provides technical requirements for accessible PDF documents. They can also support document requirements under Section 508 in applicable U.S. federal contexts.
However, a tagged PDF does not automatically guarantee full PDF/UA or Section 508 conformance. Tags must be accurate, and the completed document still needs validation and human review.
For more information about the standard itself, read PDF/UA: the global standard for PDF accessibility.
How to tell if a PDF is tagged
You can check whether a PDF has tags using a PDF editor or accessibility checker. This is a useful first step, but the presence of tags alone does not confirm that the document is fully accessible.
If you are using Adobe Acrobat, open the Tags panel. If the document contains a tag tree with elements such as headings, paragraphs, lists, and tables, it has been tagged. An empty or missing tag tree usually indicates that the document is untagged.
You can also use a browser-based checker such as GrackleGO to review the PDF’s tag tree and assess its structure. This can help identify issues such as missing tags, incorrect reading order, or improperly structured tables.
When reviewing a tagged PDF, look beyond whether tags exist. Check whether they reflect the document’s actual meaning and organization:
- Are headings tagged in a logical hierarchy?
- Does the reading order make sense?
- Do meaningful images have useful alternative text?
- Are tables structured with appropriate headers?
- Do links have descriptive text?
- Are form fields clearly labeled?
How to tag a PDF
The process for tagging a PDF depends on the document’s source, structure, and complexity. The simplest files may need only an automated starting point and a quick review, while forms, complex tables, and heavily designed reports often require more manual intervention.
With Grackle PDF, you can upload a PDF in your browser and use AI auto-tagging to create an initial structure. The tool is designed to identify reading order, headings, paragraphs, lists, tables, and images while preserving the document’s visible branding and fonts.
After auto-tagging, review the output and address any remaining issues. Automation can provide measurable uplift, but human review remains important where meaning depends on context; including alternative text, reading order, complex tables, and interactive forms.
For a closer look at automated workflows, see understanding auto-tagging of PDF documents. You can also explore easy PDF tagging with Grackle PDF for an overview of the platform.
What about scanned PDFs?
Scanned or image-only PDFs need optical character recognition (OCR) before tagging can work effectively. OCR creates a text layer that gives auto-tagging tools real text to interpret.
OCR is only the first stage. Recognition errors, incorrect columns, and unclear table structures can still affect the final document, so review is necessary before publication.
Create a tagged PDF in your browser
Creating a tagged PDF does not need to begin with a complex desktop workflow. Browser-based auto-tagging can help your team establish document structure quickly while preserving the visual design your readers recognize.
Get started with Grackle PDF to try PDF tagging on your own document.
