Overview
This error occurs when non-image elements (like lines, decorative graphics, or text boxes with special effects) are improperly tagged / not tagged at all. Our OCR output was set to "Editable text and images," effectively splitting the textbook scan into text and the page and crease of the pages into images. To get rid of this error, simply retag the document (All Tools -> Prepare for Accessibility -> Automatically Tag PDF). This will clear the error of missing alternative text. We can then edit the Tags (covered in the Acrobat Advanced Training), and add alternative text, or make the page images decorative so they will not be read by a screen reader.
To avoid having to resolve this error tag your PDF before checking for accessibility, but after doing OCR.
Steps
- Complete any OCR conversions needed and set output to Editable Text and Images
- Select Prepare for Accessibility, then Automatically Tag a PDF
- This will pop up the Accessibility Tags Pane automatically once the document is scanned.
- In the Prepare for Accessibility Pane (All Tools -> Prepare for Accessibility) select Add Alternative Text, select OK
- Use the navigation arrows to find the element that caused your error. Here you can either add alternative text if it is a graphical element, or an image. If it is simply an artifact of the scanner, you can mark it as decorative. Marking it as decorative will allow the screen reader to skip over the element.
