What is an accessible PDF?

Braille Works
4 min readAug 4, 2022

At a glance:

  • An accessible PDF gives people who can’t see, or have a hard time seeing, access to information in the PDF.
  • PDFs aren’t automatically accessible; they have to be made accessible.
  • Technology helps people who can’t see, or have other disabilities, get information from a PDF.
  • PDFs are made up of layers; the layer we see isn’t the layer computers read.
  • Steps must be taken to make all the PDF layers readable to people with low vision, blindness, and other disabilities.

Why do we need accessible PDFs?

We’ve all come across a PDF at least once or twice. But, most of us don’t know that a PDF needs to be accessible-let alone how to make one accessible.

When you look at a PDF, it looks fine. Doesn’t it?

It’s clear where the headings fall. Paragraph chunks are pretty self-explanatory. The reading order makes sense. Even the images look great and on-brand!

So what’s the problem?

Computer programs, called assistive technology, read digital information to people who can’t see it. The information that the assistive technology reads needs to be set up a certain way. Otherwise, it won’t be able to read it or may even misread it.

Assistive technology reads websites, emails, documents, and other digital information.

Many of us don’t know who’s reading our information, so it’s crucial to provide an option everyone can read. Accessible PDFs do just that. An accessible PDF allows people to read information with their eyes or computer.

Another reason you need accessible PDFs? For many, it’s the law.

Related: The Department of Justice Provides Guidance on Web Accessibility (including PDFs)

Still shot from the movie, Shrek, with Shrek explaining that ogres are like onions to Donkey

PDFs are like onions…

Contrary to popular belief, what you see in a PDF isn’t all that’s there.

Did you know that PDFs have layers? Onions have layers, ogres have layers, and PDFs have layers.

An accessible PDF has 3 of them!

  • The first layer is the visual layer. This is what sighted people see and read.
  • The second layer is the content layer. This holds all the content from the visual layer.
  • The third layer is the tag layer. This is what computers, screen readers, and other assistive technology read.

All layers are important in their own way.

The tag layer matters a lot.

This is arguably the most essential part of making a PDF accessible.

What is a PDF tag?

A PDF tag identifies each component of the document. For example, a tag tells assistive technology if it’s reading a heading, paragraph, table, or anything else in the document.

This allows assistive technology to read the information in the proper order and helps the reader skim the document by jumping through headlines or table headers.

Three layered PDFs. The first one says visual layer, second says content layer, third says tag layer.

Why do I have to create a PDF tag?

The third layer of a PDF doesn’t automatically match the first, visible layer.

When you “Save As…” or “Print” to PDF, the system doesn’t create an accurate tag layer.

The PDF needs “tags” to show the correct reading order. Otherwise, assistive technology won’t be able to read the information in the right order. It may also not be able to read the information at all.

Sure, you could run the Adobe Checker or use Microsoft Word’s Accessibility functions to create a “more accessible” PDF. But, chances are the PDF won’t be fully compliant.

A truly accessible PDF undergoes a process where both a computer and a person check to ensure the information in the PDF’s third layer is in the correct order. This process is called tagging.

  • Computers check tags, add common tags, and run diagnostics.
  • People tag complex information and check the computer’s work. (You’d be surprised how much computers miss.)

The combination of manual and automated tagging processes provides the most efficient and accurate accessible PDF.

The content layer matters too.

If you created your PDF on a computer, chances are the second PDF layer, or “content layer,” is fine.

However, if you scanned a document as a PDF, you may only have an image of text in your second layer. An image of text is readable by a sighted person but not by assistive technology. So without readable content in your content layer, there’s nothing for assistive technology to read.

Importance of an accessible visual layer.

Even though the visual layer of a PDF isn’t what computers read, it still needs to be accessible.


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This post was written by Braille Works.

Originally published at https://brailleworks.com on August 4, 2022.



Braille Works

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