In this article, we will explain what you can do to increase the accessibility of your PDF, especially for users with visual impairments. Such users often use screen readers for assistance to read the text aloud. One of the best and most popular tools on the market to make changes to PDFs is Adobe Acrobat Pro (Keep in mind that Adobe also produces the Adobe Acrobat Reader which is great for viewing but has no editing capabilities!) For all tips below, we have added paths relevant options in Acrobat.
Below we give 6 tips that will greatly improve the accessibility of your PDFs:
- Use selectable text
- Add alternate text to images
- Check the reading order
- Add tags to indicate heading structure
- Set up a meaningful title
- Specify the document language
Finally, we will show you where you can find resources to verify the accessibility of your PDFs.
Use selectable text
This is the most important step in making your document readable by assistive technology. If your textual content is encoded in images in your PDF, then screen readers cannot process it. Your image containing text like “This is a bit of really important text!” might as well be an image of the galaxy as far as the screen reader is concerned.
The best way to make sure your text is selectable is right at the source. You (or your designer) probably create your content in a tool like InDesign, QuarkXPress, or Microsoft Publisher. All these solutions are capable of exporting selectable text.
If it is not possible to generate a PDF with selectable text, then you can convert image-based text to selectable text by using optical character recognition in many cases. In Adobe Acrobat, select Tools > Enhance Scans > Recognize Text > In This File.
Add alternate text to images
Of course, almost all your PDFs will contain images. These generally come in two kinds: decorative elements and actual images. For actual images, users who cannot see properly rely on you to provide an alternate text that describes the content of the image. This alternate text should be short and clear; conveying the important information but not overburdening the reader at the same time.
In Adobe Acrobat, Select Tools > Accessibility > Set Alternate Text. You can set alternative text or indicate images as decorative.
Check the reading order
Users without any reading disabilities have no problem reading and processing texts. They can go from top to bottom and left to right (or right to left for some languages). Text in sidenotes is easily recognized as such. If a page contains several columns, then they visually recognize this with ease and understand where to continue reading. But visually impaired users don’t have that luxury. They depend on the reading order specified in the document, which screen readers use to read the content aloud to the user. The default reading order is not always the same as the logical reading order!
In Adobe Acrobat, you can select Tools > Accessibility > Reading Order to check and correct it.
Add tags to indicate heading structure
You probably use things like headers and subheaders to organize your content. Users without visual impairments recognize those easily, but people with visual disabilities need additional descriptive information in the form of tags. Make sure your PDF contains the correct navigational elements like headers for chapters and tables, and also that they are tagged as such. If the PDF is logically ordered, then screen reader users can process the information in it without difficulties. Also, people who depend on the keyboard rather than the mouse to browse PDFs will be able to navigate the document with ease. This is especially important for navigating long and complex documents, such as textbooks.
In Adobe Acrobat, you can check if a PDF is tagged or not in File > Properties > Description (look in the Advanced section). If it is not tagged, then you can add tags in Tools > Accessibility > Autotag Document.
Set up a meaningful title
PDFs are usually automatically generated by other software (like Adobe InDesign, QuarkXpress, or Microsoft Word). Not all software generates meaningful document titles, or sometimes doesn't set a title at all. A title helps your users in identifying the document, and without a meaningful document title, some users might not know they have the correct document. To specify a title in Adobe Acrobat, go to File> Properties> Description.
Specify the document language
A simple but important step is selecting the correct language for your PDF. A defined document language helps assistive technologies render text more accurately. Additionally, screen readers can load correct pronunciation rules, while visual browsers can display characters and scripts correctly.
In Adobe Acrobat you can specify the language in File > Properties > Advanced > Reading Options.
How to verify PDF accessibility?
If you followed the tips above, then you have gone a long way to make your PDFs accessible for everyone. If you’re really serious about accessibility and meeting industry standards like ADA Section 508 or the AA-level of WCAG, then you can also use automated tools to check and improve your PDF.
- PAC 3 is a free desktop tool to check the accessibility of your PDF. It is a stand-alone tool, so you don’t need any other software.
- CommonLook offers a free Accessibility Validator Plugin for Adobe Acrobat which works with both Acrobat Standard and Pro.
- Adobe Acrobat has a built-in Accessibility Checking Tool too in the Pro version. This article describes how to use it
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