It is necessary to add alternate text for all images in a document. The alternative text is read by screen readers and also is seen onmouse-overs for web images.
While in TouchUp mode, you can add alternate text to images that have been tagged using the TouchUp Reading Order tool. To add alternate text, right-click on the tag number box and select Edit Alternate Text…
Figure 1: Edit Alternate Text
Figure 2: Enter Alternate Text
An alternate text dialog box will appear. Provide your text description and click OK.