Adding alternative text will make the images in your Adobe Acrobat documents more accessible to people who have visual disabilities. However, when you use a decorative image, the image does not any valuable information. To ensure that this kind of image is skipped by a screen reader, you should mark it up as a background object.
Adding alternate (alt) text to your images will make your Microsoft Word documents more accessible to people who have visual impairments. This will also make any PDF documents created from your Microsoft Word documents more accessible as well.
The alt text is a description of the image that can be read to someone who has a visual impairment by screen reader software.