PDF How To: Add Alternative Text

Why do I need to add alternative (alt) text?

Alt text gives screen readers the words to describe your images and helps keyboard users who tab through your content—when they land on an image, they’ll hear (or see) its description. Without alt text, images get skipped or announced by their file names, which can be confusing.

What counts as alt text?

Informative images (charts, photos, diagrams) need a short description that conveys their purpose.
Decorative images that don’t add meaning (borders, spacers) should be marked “decorative” so screen readers ignore them.

Source Files

It’s best to make your original source file (e.g., Word, InDesign) accessible before converting it to a PDF. Word and InDesign can add these tags automatically when you export to PDF, and you can tweak them in Acrobat. Always double-check that every element is tagged and your document’s structure is correct.

View how to add titles to source files.

Word

Right-click (or Ctrl-click) the image and choose Format Picture.
In the sidebar, expand Layout & Properties, then Alt Text.
In the Title field, enter a short name (optional).
In the Description field, type your alt text.

InDesign

Use the Selection tool to click the image.
Go to Object > Object Export Options.
Click the Alt Text tab.
From Type, choose Custom and enter your text.

Adding Alt Text in Acrobat Pro

Open your PDF and select the Tags option from the Navigation Panes list on the left side of the screen. This will open the Tags Tree. Note: If the tags option is not visible, right-click in the toolbar and choose the Accessibility tags option; this will add it to your toolbar.
Screenshot of Sample Document in Adobe Acrobat DC with the Tags Panel open and an image of a person with a white cane walking in front of a buildings selected.

Within the Tags List, right click the <Figure> you want to add alternative text to. Choose the Properties option from the menu.

Screenshot of Tags Panel with Figure selected and Properties selected in menux.

In Object Properties menu, type your descriptive alternative text into the edit box for Alternate Text. Include the most important information first and be as concise as possible. To save changes, choose the Close button.

Screen shot of Object Properties dialogue box with alternative text in the Alternate Text field.

Recommendations

Follow these best practices when writing alt text:

Be accurate and equivalent: Convey the same information the image provides.
Be succinct: Keep it short, usually under 125 characters.
Avoid redundancy: Don’t repeat nearby text.
Skip “image of…” or “graphic of…”: Screen readers already announce it’s an image.

Additional Resources:

One Stop: Core Topic Alt Text

WebAIM: Alt Text Introduction

Social Security Administration: Alt Text Guide pdf