Knowing the requirementsCheck accessible PDF documents

Checking digital accessibility cannot be done by machine alone. Machine checking is particularly suitable for the technical aspects of PDF accessibility. However, it cannot replace the final check by a human. PAC supports both.

Check all requirements with PAC

The Matterhorn protocol: the PDF/UA test protocol, shows two thirds of the requirements can be checked automatically. The remaining third requires assessment by a human.

There are basic requirements that apply to all accessible PDFs and use case-specific requirements that only apply to certain content - such as tables, formulas and links.

With PAC, you simply check the technical requirements automatically in a matter of seconds and then use the visual check functions such as screen reader preview and structure view to complete the check.

The five basic requirements

An international working group of the PDF Association has formulated five basic requirements (the so-called "Fundamental Techniques") that apply to every accessible PDF. You can check them all with PAC.

Basic requirement 1: PDF basic rules are complied with

In order for software to successfully process accessible PDF files, the basic technical rules for "Tagged PDF" must be adhered to. "Tagged PDF" is a special mechanism for providing structural information in a PDF. The rules for this mechanism are defined in the corresponding PDF specifications. These include ISO 32000, the specification for PDF itself, and ISO 14289, the specification for accessible PDF documents (PDF/UA for short), which supplements the requirements of ISO 32000. Compliance with these basic rules can be checked with the help of PAC.

Basic requirement 2: Machine-readable content

Machine-readable text content is an essential basic requirement for accessible PDF documents. Only such content can be presented by software in an alternative form for users with special requirements - for example as audio or Braille output. On the one hand, there are therefore special requirements in PDF for the machine readability of text content. On the other hand, non-text content that is to be perceived as text by both software and users (as in a scanned document, for example) must be provided as machine-readable text content.

Basic requirement 3: Distinguish between real content and artifacts

A PDF may contain elements that are not important for understanding the content. For this reason, PDF distinguishes between two categories of content elements: there is real content (the technical term for this is "real content") and artifacts. Content elements that are supposed to be real content must be identified with the help of a tag. For artifacts, on the other hand, there is a separate tag called "artifact".

Basic requirement 4: Logical content sequence

In addition to labeling the real content using tags, the order of the content in the tag tree must be defined in a suitable way so that software (including assistive technology) is able to display the content correctly. The term for this is logical content order. This must reflect the author's intended order of the actual content.

Basic requirement 5: Appropriate semantics

A PDF document has appropriate semantics if it contains suitable tags that enable software (including assistive technologies) to distinguish between elements of real content (e.g. headings, paragraphs, lists) and provide information important for understanding that would otherwise only be conveyed by the visual appearance (e.g. layout, font size, font color). Appropriate semantics also means that related content elements that are visually separated (e.g. by a page or column break) can be recognized as such in the tag tree.