PDF Tagging & Accessibility SDK

Generate tagged PDFs and create accessible documents.

With the GdPicture.NET PDF SDK you can generate tagged and accessible PDFs from scratch. Be careful, not all tagged PDFs can be considered accessible.
The PDF/UA standard describes the technical specifications to generate and validate fully accessible and ISO compliant PDF files.

Tagged PDF


Tags are structural elements of the PDF that describe the document’s logic.

According to the PDF specification, “it defines a set of standard structure types and attributes that allow page content (text, graphics and images, as well as annotations and form fields) to be extracted and reused for other purposes.”

The logical structure

The logical structure of the document consists of the organization of the document into chapters and sections.
Special elements such as figures, tables, and footnotes are also mentioned.

Tags can hold supplementary information about images, figures, tables, like their titles, or some useful descriptive text.
They can store information about sections, paragraphs, like their heading, naming, as well as their font size or font style.

They also allow distinguishing between the real page content and some graphical items not relevant to the contained information.

Read more

Screenshot of a tag tree


PDF/UA is the ISO standard for Universal Accessibility

ISO 14289 describes the technical specifications for creating, viewing, and using accessible PDF files, for publishers of PDF software and assistive technology. It also lists validation elements for PDF/UA compliance.

Accessibility is a social necessity for people with disabilities and a legal necessity in many countries.

PDF/UA is compatible with long-term archiving (PDF/A).

PDF/UA validation

As it is difficult to say if a PDF is accessible just by looking at it, it is necessary to make some tests to validate the PDF/UA conformance.
There are two types of tests:

  • Automatic validation with the help of different programs.
    Here is a list of different programs for PDF/UA validation and accessibility checking.
  • Human validation controls the results and ensures that the semantic, logical, and language aspects are met and errors are corrected.

Benefits of tagged and accessible PDFs

  • It’s easier to extract text and graphics from a tagged document.
  • It helps tools to process text for searching, indexing, and spell-checking purposes.
  • It preserves the document structure for conversion to file formats such as HTML, XML, and text documents.
  • Well-tagged PDFs can reflow and their content can fit different screens or mobile devices better.
  • They are screen-reader friendly for people using assistive technologies.
  • Tags are necessary to achieve section 508 compliance.
  • PDF/UA conformance validates several accessibility requirements for the Web, WCAG 2.0.
  • Tagged PDF provides a solution for semantic reuse of PDF content, which can help with the redaction process.

How to use

The GdPicture methods to tag and generate accessible PDFs:

Download and install GdPicture.NET package from here.

You will find a compiled demo applications in
[Install directory]\Samples\Bin\

You will be able to find C# and VB.NET demo applications including source code in
[Install directory]\Samples\WinForm\

You will find other code snippets within the online reference guide found here

You can find some discussions about PDF in the dedicated section of our community forums located here

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