WebAIM - Web Accessibility In Mind

PDF Accessibility
Acrobat and Accessibility

Introduction

Adobe Acrobat Professional is the most commonly-used program to evaluate, repair, and enhance the accessibility of existing PDF files. This article outlines accessibility features and best practices in Acrobat DC and XI.

Set Up Acrobat

The two most important tools for reviewing and repairing PDF accessibility are the Tags pane and the Accessibility tools pane. They are both hidden by default in Acrobat, so you will need to go through a one-time process to make these tools visible and available.

To open the Tags pane for the first time, select View > Show/Hide > Navigation Panes > Tags.

The Tags pane will appear in a sidebar on the left side of Acrobat. To show or hide this pane in the future, click the "Tag" icon in on the far-left side of the window.

To show the Accessibility tools pane for the first time, click the Tools tab in the upper-left of the window (not the Tools pane on the right side). In the search bar below the tab, enter the word "accessibility". When the Accessibility tools appear, click the Add button.

Go back to the PDF you are working on and you will now see Accessibility in the right-hand sidebar. Click it to open a group of accessibility tools.

Note:

To show the Accessibility Tools for the first time in Acrobat XI, open the Options menu ( screenshot of options menu ) in the upper-right corner of the Tools sidebar and select Accessibility to make it visible, then click Accessibility to expand this section.

You will likely move between the Tags pane and accessibility tools multiple times while repairing a PDF.

Tags Pane

PDF "tags" determine the order and structure of PDFs for screen reader users, and the Tags pane allows you to view, reorder, modify, create, and delete these tags.

This pane displays all the tags within the PDF, organized in a tree structure. This tags tree can be navigated, expanded, and collapsed using a mouse or the arrow keys on the keyboard. Many of the tags are similar, if not identical to tags in HTML. The most notable difference is <Figure> tag, which is like the <img> tag in HTML.

Screenshot of the tags pane

Selecting a tag should highlight the corresponding text, image, or other element in the PDF file.

Add tags to an untagged document

If the tags pane shows "No Tags available" and you do not have access to the source document used to create this PDF, you will need to add tags to this document. To add tags to an untagged document that contains text, choose the Options menu in the Tags pane, then Add Tags to Document. You will need to review the generated tags and usually do some repairs, but that is almost always easier than creating the entire tag structure manually. This is especially true if the document contains tables or lists (assuming Acrobat creates the correct tag structure). If file is a scanned PDF that does not contain text, you must first extract the text in the PDF, as outlined later.

Find Tag from Selection

Just as selecting a tag highlights the content in the body of the PDF file, there is a way to accomplish the opposite effect of highlighting the tag that corresponds to selected content. First, click on the Selection Tool (Select tool icon). Next, select the object. Finally, go the Options menu at the top of the Tags pane and then select Find Tag from Selection.

This will highlight the tag or tags that contain the selected content.

Create Tag from Selection

At times, you will encounter a PDF file that has missing or incorrect tags. It is often easier to repair these tags using the Reading Order tool outlined below, but there are some actions that can only be accomplished in the Tags pane.

If choosing "Find Tag from Selection" does not highlight a tag in the tree, the content does not have a tag associated with it. To create a tag for the selected content, click the Options menu and select Create Tag from Selection.

Change and delete tags

To change a tag from one type to another, right-click the tag you want to change, and select Properties. Click on the Type dropdown and select the desired tag.

Screenshot of the dropdown list to change a tag.

To delete a tag from the tree, click on the tag, or navigate to it with the arrow keys, and press Delete. Make sure the tag that you are deleting does not contain any content that you want presented to a screen reader.

Reading Order Tool

The Reading Order tool—called Touch Up Reading Order (or TURO) in older versions of Acrobat—helps you add and edit many common PDF tags. To use this tool, go to the Accessibility tools and select Reading Order (or Touch Up Reading Order in Acrobat XI). A dialog will appear.

The appearance of the PDF also changes—the content will become encased in numbered gray boxes.

If you don't see any boxes, your PDF document is most likely untagged.

View "Structure types"

By default, each of these gray boxes are numbered to represent the content order of the PDF, but it is best to worry about the structure of the PDF first, then its reading order. To see the tag structure instead, choose the Structure types radio button in the dialog.

This will change the view so that the white boxes in the upper left corner of each element displays the tag type (e.g., "P" or "H1") instead of the numbers.

Screenshot of the structure of PDF including headings, a list, and a table.

Add & Change tags

Important

You cannot undo changes made with the Reading Order tool. Save often!

To add or change a tag, use the crosshairs () to draw a box around content you want inside this tag. It is sometimes difficult to select exactly the right area, but it is a little easier if you try drawing a box that is slightly larger than the content. If there is already a gray box around the element, and you just want to change the tag (e.g., changing a heading level), try clicking on the tag in the in the top-left corner of the box. This should select the box, but the behavior can be a bit buggy. You will probably need to switch between these two techniques while repairing a PDF.

After selecting the area, choose the desired tag from the Reading Order window.

Reading Order tool tagging options
Button PDF Tag Additional information
Text/Paragraph
(Text in XI)
<P>  
Form Field <Form>  
Heading 1-6 <H1>-<H6>  
Figure <Figure>  
Figure/Caption <Figure> <Caption> If you select the image and adjacent text then the image will be tagged as a figure and the text will be tagged as its caption.
Table <Table>, <TR>, <TH>, and <TD> Acrobat attempts to assign rows, columns, and headings. Sometimes it does this correctly, but this should still be checked with the table inspector.
Cell <TD> Can be used to merge cells if they are incorrectly split.
Formula <Formula>  
Background/Artifact
(Background in XI)
Artifact This will hide an item completely from a screen reader. It can be used on images and text.

If you do not see an option for your desired tag, you will need to create it manually in the Tags pane.

Tip

It is often best to remove existing tags a specific item or area before assigning new ones, especially for buttons that create multiple tags like "Table." To remove the structure from an area on the page, select it as outlined above, right-click, and select Delete Selected Item Structure . To clear an entire page, select the Clear Page Structure… button in the tool dialog. You can then select items and assign the proper tags.

Alternative text

When an image is tagged as a figure, the alternative text will appear in a black box in the upper-left corner of the image. If it has no alternative text, the caption will read "Figure - No alternate text exists."

To add or edit alternative text, right click on the image and select Edit Alternate Text. Enter the appropriate alternative text in the dialog box.

Table Inspector

The Table Inspector allows you to easily identify, create, and repair table headers.

With the Reading Order tool open, select a table and then select Table Inspector. Click and drag to select a group of the column or row headers. Right click on the selected cell or cells and choose Table Cell Properties.

A dialog box will appear. Select the Header Cell radio button, then select the Scope menu and choose Row or Column (never choose "Both" or "None").

After selecting OK, you will notice that the table header cells are highlighted in red and the data cells will be highlighted in gray. Repeat for all the headers in the table.

screenshot of a table where the top row and the first column are highlighted in red

Tables with more than one level of row or column headers, or with cells that span multiple rows or columns, may need extensive work to ensure they are presented correctly to screen readers. Whenever possible, simplify your tables to avoid this overhead. If the table structure is very poor, it may be easier to have Acrobat re-tag the table automatically. Click outside the table to exit the Table Inspector, then select the right-click, and choose Delete Selected Item Structure. Draw a box around the entire table and select the Table button. The quality of the tags for a table can vary greatly—Acrobat does best when the table has clear borders between each cell and no background colors.

Repair the Content and Tag Order

If you made changes to the tag structure of the PDF, you need to make sure the tag order is correct. It is natural to assume that the Reading Order tool is the place to fix this, but it is actually much more complicated than that.

Content vs. tag order

In addition to the visual reading order, there are two hidden types of "reading order" within a PDF: the tag order that is accessed by screen readers and other assistive technologies, and the lesser-known content order that is used by Adobe when a user selects Reflow (useful on mobile devices) or Read Out Loud options.

Important

The Reading Order tool displays the content order of the PDF, NOT the tag order.

In other words, even if the order of the numbers in the Reading Order tool looks correct, the PDF may still be read incorrectly by a screen reader. The reverse is probably even more common—in most PDFs created from Word documents, images are placed in the correct place in the tag order, but they typically come at the end of each page in the content order. While the goal is to get the content and tag order to match the visual order, the tag order takes priority in accessibility repairs because that is what will be accessed by a screen reader.

Review and repair the content order

To review and repair the content order, open the Reading Order tool and select the Page content order radio button. The tags in the upper-left corner of each content box will change back to numbers. If the order of these numbers is not correct, select the Show Order Panel button and Acrobat will open the Order pane on the left side of the window.

To change the content order, either click-and-drag the items listed or use the cut and paste keyboard shortcuts—Ctrl (or Command on Mac) + X or V).

Using this page can be confusing. While it displays the content order (not the tags order), changes made within this panel will be reflected in both the tags and content order, but this behavior can be unpredictable. It can cause discrepancies between content and tags order, and even break order that was previously correct, so changes made in the Order pane should be completed first and then verified in the Tags pane.

Review and repair the tag order

To check the order of the tags in the PDF, open the Tags pane. Like the Order pane, either click-and drag or with the mouse or cut and paste with the keyboard to change the order. When moving tags around, make sure the nesting of the tags within the tree stays correct.

Other Tools and Features

Accessibility Checker

The built-in accessibility checker "Full Check" is a good tool to use with a new PDF to identify what issues need to be addressed, and after repairing a PDF to ensure no obvious issues were overlooked. To run the checker, select Full Check from the Accessibility tools pane. The results will appear in the "Accessibility Checker" Pane on the left side of the window.

For additional information about an issue, right-click it and select Explain, and Acrobat will direct you to online documentation that outlines the issue, and often tells you how to fix it.

The Accessibility Checker cannot identify all accessibility issues. You should also manually check the document for other potential issues.

Set Alternate Text

To add alternative text to multiple images, go to the Accessibility tools and select Set Alternate Text. The first image in the file will be highlighted, and a dialog box will appear with a space to enter the alternative text. Enter the appropriate alternative text and press the right arrow icon to move to the next image.

There is also a checkbox to identify an image as a Decorative figure. Unfortunately, this feature does not work as it should. If you check this box and run the Accessibility Full Check again, the error for the image will change from "Figures alternate text - Failed" to "Other elements alternate text - Failed." Until this bug is resolved, do not use this checkbox to hide decorative images. Instead, skip over these images by pressing the right arrow button to skip to the next image. After adding alternative text to all the images that need it, select Save & Close. Then use the Background/Artifact button in the Reading Order tool to hide any images that should not be read by a screen reader.

Convert Scanned Text

Before you can create a tagged PDF, you must first ensure that the PDF contains real text. If it does not, you must either recreate the PDF file (if you have the source document) or convert it to include true text. To add this tool, go to the Tools tab and find add Enhance Scans. Return to the PDF, select Enhance Scans in the Tools pane, then in the toolbar above the PDF, select Recognize Text > In this File.

The quality of the text depends on the clarity of the source document. To clean up any text that Acrobat had trouble detecting, select Recognize Text > Correct Recognized Text (called Find All Suspects in Acrobat XI).

Reflow

The Reflow view allows users to reorder the content of a PDF into a simplified, single-column layout, based on the content order.

Select View > Zoom > Reflow or Control + 4. If the document does not appear in the correct order while in Reflow view, fix this using the Order pane, as outlined above.

Read Out Loud

Read Out Loud is a text-to-speech tool that is available in Adobe Reader and Acrobat. Because it reads the PDF based on the content order, it is not an acceptable substitute for screen reader testing.

"Make Accessible" Action Wizard

Acrobat Action Wizards automate common multi-step processes in Acrobat, including several common steps in creating an accessible PDF.

The "Make Accessible" action Wizard can be a useful tool, especially when starting with scanned or untagged PDFs. It is a helpful way to ensure that you don't miss any steps while making your document accessible, like providing a page title or document language. To run the wizard, use the Tools tab to add Action Wizard (it should be visible by default in Acrobat XI), then Open Action Wizard and choose Make Accessible. The wizard will then run you through several steps:

  1. Add Document Description
  2. Set Open Options
  3. Recognize Text using OCR
  4. Detect Form Fields
  5. Set Tab Order Property
  6. Set Reading Language
  7. Add Tags to Document
  8. Set Alternate Text
  9. Run Accessibility Full Check
Important

If your PDF is already tagged (e.g., you created a PDF using instructions on the previous page) you must skip step 3: "Recognize Text using OCR." Otherwise, your PDF will be re-tagged, and the new tag structure is seldom as good as the original. To skip this step, preferably before you start the wizard, right-click the Recognize Text using OCR option and select Skip This Step.

You will still want to check your PDF after using this wizard. For a video walkthrough and handout on the "Make Accessible" Wizard, see the GOALS Acrobat cheatsheet.