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Understanding the Accessibility Barriers and Spectrum of PDFs

Written by

Shannon Hauser

Published on

When we talk about making PDFs accessible, it can sound like a single, straightforward task. In reality, PDFs exist on a spectrum. Where a PDF falls on that spectrum has a major impact on how accessible it already is and how much work it will take to remediate. Before talking about the specific kinds of PDFs it is important to understand the major accessibility barriers with PDFs.

Three Major Accessibility Barriers in PDFs

Most PDF accessibility challenges relate to the same underlying elements. If any one of these is missing or incorrect, the PDF may be difficult or impossible for someone using a screen reader or text-to-speech tool to use.

OCR (Optical Character Recognition)

OCR converts images of text into actual, readable text. You can tell if a PDF has OCR because you’ll be able to highlight/copy the text or search within the PDF for words. OCR answers the most basic question: can the text be read at all?

Why OCR matters:

Screen readers and text-to-speech software can only read text, not images. Without OCR, a scanned PDF is effectively unreadable to assistive technology.

Common Issues:

  • Many scanned PDFs have no OCR at all.
  • Automatic OCR can introduce errors, especially with poor scans, math, or older documents.

Tags (Document Structure)

Tags provide the underlying structure of a PDF. They communicate what each part of the document is and how it is organized.

Why tags matter:

  • Tags identify headings, paragraphs, lists, tables, and images.
  • They allow screen reader users to move through a document efficiently rather than listening from beginning to end. For example:
    • Headings allow users to jump between sections, much like skimming a document visually.
    • Tables can be read by row and column, with context preserved.

Common issues:

  • Many PDFs are untagged or incorrectly tagged.
    • Elements like tables, figures, and lists are often missing usable tags

Reading Order

Reading order controls the sequence in which content is read aloud. Typically assistive devices follow the tag order to know what order information should be read aloud.

Why reading order matters:

  • Screen readers and text-to-speech software follow the programmed order, not the visual layout.
  • A document that looks fine visually can be confusing or meaningless when read aloud.

Common issues:

  • Multi-column layouts are read out of sequence.
  • Sidebars, footnotes, captions, and headers interrupt the flow.

How These Barriers Show Up Across Different PDFs

Below are some common PDF examples and how these accessibility barriers tend to appear in each.

Scanned PDFs (Image-Only PDFs)

These are PDFs created by scanning a physical document. They are often created using a copier or phone camera/scanning app. They tend to be only images of page, not text.

Accessibility challenges:

  • No OCR, so text cannot be read at all
  • No tags or document structure
  • No reading order

These PDFs usually start with none of the three core accessibility elements in place, which makes them the most difficult and time-consuming to remediate.

Scanned PDFs With OCR Applied

Some scanned PDFs have OCR applied automatically by a scanner or software. They are still image-based but they have a machine-generated text layered over the images.

Accessibility challenges:

  • OCR errors are common and must be corrected
  • No tags so there is no document structure.
    • Images, charts, and tables may have some of their text read but will be meaningless because of lack of tags
  • Reading order will not necessarily be logical

OCR helps with basic access, but structure and meaning still need significant work.

Publisher or Journal Article PDFs

These are PDFs provided by academic journals or publishers, often made available through library resources. Usually born-digital PDFs designed for visual reading. Often include columns, footnotes, figures, and complex layouts.

Accessibility challenges:

  • Tags may be minimal, inaccurate, or missing entirely. Some examples include:
    • Images, charts, tables without alt text descriptions
    • Headings not properly identified or nested properly
  • Some text, like math formulas, are difficult to make accessible in PDF format
  • Complex reading order due to columns and side content

We should expect over time that publishers and journals will be working towards making their PDFs more fully accessible, but this will take time.

PDFs Exported From Word, Google Docs, or PowerPoint

These are PDFs created by exporting a document written in a word processor or slide tool. They are born-digital documents PDFs, often instructor-created.The text is natively searchable, selectable, and editable.

Accessibility challenges:

  • Original document not tagged properly in Word, Google Docs, or PowerPoint. For example:
    • Headings applied visually instead of structurally
    • Missing alternative text for images, tables, graphs
  • Some text, like math formulas, are difficult to make accessible in PDF format
  • Improper export settings that don’t include the tags in PDF export

These PDFs are often the easiest to remediate, especially if the original source document is available.

Before You Start Remediating

Remediating a PDF for accessibility can take time and effort, so it’s worth pausing to make sure it’s the best option for your class. Ask yourself first:

  • Do you really need this file? This is a good time to re-evaluate course materials in general. If newer sources are needed or it isn’t essential to your learning objectives anymore consider removing it entirely.
  • Is it available in another format? Does the same information already exist in another format? Sometimes an accessible Word doc or HTML version works better. If students are seeking different formats encourage them to use the alternative formats generator inside Panorama to create a different format from your original document.
  • Can you link to a library resource? Linking directly to a library resource may provide a more accessible version of your reading. See the library guide on permalinks for more details. Simpson Library staff will also work with faculty who are trying to find more accessible versions of their course materials. Please reach out to them at umwlibaries@umw.edu.
  • Can you convert this PDF? Is this PDF suitable for converting to a more accessible format (HTML, Word, Canvas page) to share with students? YuJa Panorama can generate some alternative formats that can be used to replace original document.
  • Is your current PDF suitable for remediation? If document is from a scan from physical book or paper check to see if the document is blurry or crooked, re-scanning may be a necessary first step. If you can find a born-digital version of the text this is the best place to start from. If you need a new scan of a text and the item is in the library’s collection you can put in a digitization request for a new scan to be made.

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