It is important to make PDF documents and forms accessible to individuals with disabilities. To help, Adobe Acrobat Professional has two separate accessibility checks that it can perform. They are called the Quick Check and the Full Check. One of them should be avoided.
The Quick Check for accessibility in essence is only checking to see whether your PDF has tags. If tags are present, you’ll see the message “No accessibility problems were detected in this quick check.” There may be lots of accessibility problems with the document or form, but the Quick Check still says there are none because it only checks for the presence of tags.
Please don’t use Quick Check to decide whether your PDF document or form is accessible.
Instead, use Full Check. It is not going to find all issues, but it is better than Quick Check. It can identify when alt text is missing from a graphic and other basic issues. It also offers hints on how to repair some errors.
To launch a Full Check in Acrobat Pro versions 7 to 9: Advanced menu > Accessibility > Full Check
To launch a Full Check in Acrobat Pro X: View menu > Tools > Accessibility > then in right sidebar Full Check