Essentials for PDF accessibility

Adobe created the PDF in the early 1990s, as an agnostic file format to accurately render, read and print documents, no matter the software or operating system. Its prime goal was to allow file sharing across and between companies, while strictly maintaining the document structure and integrity.

“What industries badly need is a universal way to communicate documents across a wide variety of machine configurations, operating systems and communication networks. These documents should be viewable on any display and should be printable on any modern printers. If this problem can be solved, then the fundamental way people work will change.”

~ John E. Warnock, cofounder of Adobe

The most extraordinary part of the PDF story is that it’s outlasted other ‘assumed’ gold-standard technologies – both software and hardware. Many of those technologies have been replaced by newer, more modern solutions, whereas the ubiquitous PDF remains a stalwart file format across the digital world.

Curiously, it’s the agnostic characteristics that inspired PDFs, which also make it the perfect format for accessible documents and accessible PDFs. However, while they’re considered a ‘universal’ document which everyone can access through free software, they often present significant challenges to people who use assistive technology.

These barriers violate accessibility standards such as Web Content Accessibility Guidelines (WCAG) 2.0, Section 508, the ISO PDF/Universal Accessibility Standards, and the Americans with Disabilities Act (ADA) as well as other localized non-discrimination laws. These legislative rules require businesses to provide equivalent access for people with vision disabilities, cognitive differences, mobility impairments, and other conditions – or risk legal action being taken against them.

What is an accessible PDF?

An accessible PDF makes it easy for people with disabilities to access, and navigate the document, while meeting standards such as WCAG 2.0, PDF/UA and Section 508. It must be universally accessible by screen readers like JAWS or NVDA, text-to-speech tools, screen magnification and other assistive technologies, so they can easily read and navigate its content.

Other key aspects of an accessible PDF are:

• Alt text must be provided on images
• Can be navigated using a keyboard or other assistive devices
• Each page element is tagged with PDF tags to identify the type and format of content
• Content is formatted in a hierarchical structure of H1, H2, H2 through to H6 headings

What are accessible PDF tags?

PDF tags provide a hidden structure to the PDF content, which screen readers ‘read’ to navigate the document. Similar to HTML tags on web pages, PDF tags have no visible effect on the PDF file and only exist for vital accessibility purposes. Each page element in the document is “tagged” and the tags identify content as:

• Headings
• Paragraphs
• Lists
• Tables
• Figures
• etc

The tag also stores some attributes about the page element. PDF tags arrange the document content into a hierarchical architecture – a “PDF tag tree” – that forms the logical reading order of the document, which assistive technologies and screen readers follow.

What’s the difference: PDF vs accessible PDF?

A PDF isn’t inherently accessible. Generally speaking, if the source documents of a PDF aren’t structured, tagged and created to meet accessibility standards, it subsequently makes the PDF export inaccessible to people who rely on assistive technology to read and interact with online content.

The additional work required to ensure a PDF (produced from a source document) is inclusive:

• Text must be searchable
• Form fields must be labeled as interactive and include error messages
• Bookmarks are accessible using the keyboard
• Security settings can’t interfere with screen-reader capabilities
• Structural tags need to be set to define reading order
• Alt text must be included on all images
• Use of text instead of images of text
• Color cannot be solely used to convey meaning
• Color combinations must have suitable contrast between foreground and background colors

How to convert a standard PDF to an accessible PDF

• Find the source document for the PDF.
• If the PDF is created from a typed text document, the source document must be restructured so it's accessible, using WCAG accessibility guidelines.
• If the PDF is created from a scanned image, the source image needs to be located and converted to an accessible document, using WCAG accessibility guidelines.
• Any images used in the source document must include alt text.
• Create a new PDF (make sure the conversion settings are set to 'Accessible (tagged) PDF)' in the program you are using.

Generally speaking, a PDF is a second option for the creation of accessible digital content. Instead, it’s preferable that the document is added to a website or internal wiki as a web page (in HTML). If this is not appropriate, then the document should be provided in an alternative accessible format such as MS Word or Rich Text File (RTF) format.

If a Google Doc is the source document, ensure you use Google Chrome’s PDF tagger to produce the PDF.

Note: An advanced Adobe tool (like Acrobat Pro DC) can be very helpful, as it has several built-in tagging features that help identify and structure elements in PDFs – these features are not available in standard versions

Adobe, Acrobat and PDF explained

There are three Adobe (the company) Acrobat (the product) tools to create PDFs (the file format/document):

• Acrobat Reader: You can view and interact with a PDF (including the accessibility features of a PDF), but it cannot be used to create new PDFs or edit existing ones.
• Acrobat Standard: Has the ability to create a PDF, and convert a scanned PDF to a searchable file. But you cannot view or edit accessibility information.
• Acrobat Pro: This is the only version of Acrobat that can be used to view and edit the accessibility information of a PDF.

PDF accessibility standards

For PDFs, the two most frequently cited standards are:

• Web Content Accessibility Guidelines (WCAG), considered the international standards for digital accessibility. WCAG is also applicable to websites, mobile apps, and other online content such as PDFs.
• International Standards Organization (ISO) requirements for electronic document file format enhancement for accessibility is PDF/UA (ISO 14289-1:2014).

The ISO’s guide is based on WCAG 2.0. Therefore, some authors reference the ISO standards, while others directly reference WCAG, but both documents have similar requirements.