Setting the accessibility permission flag allows assistive technology such as screen readers to bypass certain security settings within a PDF. Screen readers need to be able to copy or extract a PDF's text to convert it to speech. If a document author adds security settings that specify that the document cannot be copied, printed, extracted, commented on or edited, the security settings may interfere with a screen reader's ability to read the document. 

To fix this issue automatically, right-click "Accessibility Permission Flag" on the Accessibility Checker panel. Then, choose "Fix" from the Options menu.

To fix this issue manually, open "File" followed by "Properties" and select the "Security" tab. Choose "No Security" from the Security Method drop-down list and click "OK." By default, this will allow assistive technologies to access the document's content, according to Adobe. If your document needs security measures in place, select "Password Security" from the drop-down list. In the Permissions section of the Password Security Settings dialog box, make sure the box for "Enable text access for screen reader devices for the visually impaired" is checked. This is the default setting.

A user navigates through Adobe Acrobat Pro to set the accessibility permission flag.

WCAG Requirement: 1.1.1 Non-text Content