Kacper Hoffman
PDF (Portable Document Format) is one of the most commonly used formats for presenting text, graphics, tables or forms. However, its popularity raises specific accessibility questions. Can any PDF document be considered accessible? Is it adaptable to different types of physical, sensory, and cognitive disabilities? Is it designed so that people with such disabilities can use it independently? These requirements are defined by the WCAG guidelines.
It’s also important to note that – using only assistive technologies and without the need for third-party support – users with disabilities should be able to perceive the content of a document to the same extent as users without disabilities.
So what should be considered when creating accessible PDF documents?
The WCAG guidelines define accessibility criteria for documents and websites for people with various types of disabilities. These guidelines are based on four key principles: functionality, compatibility, perceivability, and understandability.
According to the European Accessibility Act (EAA), from June 28, 2025, not only public institutions will have to comply with this standard. The new regulations will also apply to organizations that provide services over the Internet – including banks.
For more information on what WCAG is, its background, who must comply, and who benefits most, read our introductory article on WCAG.
The PDF/UA (Universal Accessibility) standard, developed by the International Organization for Standardization (ISO), and the Web Content Accessibility Guidelines (WCAG), developed by the W3C, define the principles for creating documents that ensure that everyone can access the information contained in a PDF.
Let’s look at some of these key principles.
The structure of the document should be designed to ensure its correct representation in the final PDF file. This means that all content elements – such as headings, paragraphs, lists, or tables – must be properly tagged according to the semantic rules of the tool being used. Depending on the technology for creating the document, appropriate techniques should be applied to ensure a correct hierarchy and logical structure of the content. For example:
\chapter, \section, which clearly define the hierarchy and semantics of the content.<h1>, <p>, <ul>, <table>, which specify the role of each element in the document structure.role="H1", to ensure the correct interpretation of document structure in the final PDF.<P>, <L>, <Table>, which preserve the logical structure of content and allow it to be read correctly by assistive technologies.Regardless of the tool used, it is essential that the final PDF document accurately reflects the content structure, ensuring correct processing by screen readers and other assistive technologies.
Graphics that are essential to the content-such as charts or diagrams-should include alternative text that describes their content for screen reader users. In addition, links within the document should be clearly labeled, such as “Download PDF" instead of “Click here," so that users know exactly where the link is going.
In PDF documents, maintaining proper contrast between text and background is essential for readability, especially for users with visual impairments. Contrast can be calculated using the following steps:
First, calculate the luminance of each color (text and background) using the formula:
L = 0.2126 ⋅ R + 0.7152 ⋅ G + 0.0722 ⋅ B
where R, G, and B are the color values in RGB space.
Next, calculate the contrast ratio using the luminance values:
Contrast ratio = (L_lighter + 0.05) / (L_darker + 0.05)
According to WCAG guidelines, the minimum contrast ratio should be 4.5:1 for normal text 3:1 for large text (e.g. headings)
More information: https://www.w3.org/TR/WCAG20-TECHS/G18.html
It is also important to avoid relying solely on color as a means of communication (e.g. red text on a green background), as people with color blindness may have difficulty distinguishing such elements.
To ensure that screen readers can correctly interpret text in different languages, it’s important to specify the language for the entire document, as well as for individual segments of text written in other languages. This allows the screen reader to switch to the appropriate speech synthesizer to ensure accurate pronunciation. Providing a document title can also help users locate and identify the document.
Flashing or rapidly changing elements in documents can cause unwanted reactions, such as epileptic seizures, especially in people who are sensitive to light. To minimize this risk, the frequency of flashing elements should not exceed 3 Hz.
For documents that contain multimedia elements such as video or audio recordings, it is essential to provide captions or transcripts. This ensures that people who are deaf or hard of hearing can access the audio and video content. According to WCAG 2.1 guidelines, all audio content in synchronized media must have extended captions unless the media is used as an alternative to text and is clearly labeled as such.
Supporting people with learning disabilities and cognitive limitations means using simple, clear language and avoiding complex phrases. The structure of the document should be organized and consistent, with clearly defined headings and sections. In addition, numbered lists, tables, and other learning aids can be helpful in improving comprehension.
Even when following standards and best practices, it can be difficult to determine at a glance whether a given PDF document is fully accessible. Unfortunately, there is no official tool created by the ISO committee specifically for this purpose, but there are both paid and free applications that can help by checking the document for accessibility and generating a report – and in some cases even allowing editing.
This is one of the most popular paid tools for editing and testing PDF files for accessibility. It includes a built-in “accessibility checker" that analyzes documents and highlights accessibility issues. It allows users to check document structure and applied tags, alternative text for images, and contrast. With this tool, we are able to edit the document with accessibility in mind.
PAC is a free tool that checks PDF documents for accessibility according to both the WCAG and PDF/UA standards. It provides the ability to preview the structure of the document being checked and allows users to generate summaries and detailed error reports that show where problems occur.
Screen readers are programs that assist blind and visually impaired individuals by reading aloud the text displayed on a computer screen. They work with the operating system, converting information into speech or Braille, enabling users to interact with the computer and use various programs and applications. A screen reader can read a PDF document only if it has been properly prepared for accessibility.
It is particularly important, as mentioned earlier, to correctly and logically tag elements within the document, as these tags are interpreted by the screen reader to create a hierarchy that allows users to navigate the document comfortably and understand its content. In addition to the proper structure, it is necessary to include alternative texts for images, charts, or other graphic elements, so that blind users can understand the content of the document. Without such descriptions, the screen reader will skip the graphic or read only the file name, which provides no valuable information.
Most popular screen readers:
While there are already tools to automatically check PDF accessibility, it’s also important to test the document with a screen reader. This is the only way to ensure that all elements are read correctly and that the document is fully usable by people who rely on assistive technology.
For more information on accessibility testing with different types of screen readers, see our article on WCAG accessibility testing.
When deciding to ensure the accessibility of the PDF documents, in addition to meeting legal requirements, we should also be motivated by the desire to provide people with disabilities with full and independent access to the content.
It is important to be aware of the rules that apply to the creation of such documents and to take a comprehensive approach to accessibility testing using tools and assistive technologies, such as screen readers, used by people with disabilities. By doing so, we can create PDF documents that are accessible to all users and remove barriers to information access.
