I've been looking at a number of pdfs for my institution, and have disocvered that the Full Check option in Acrobat XI (though I've seen this in Acrobat X as well), isn't marking errors for figures without alt text. It will on some files, but on most it just marks the test as passed when it should be failed.
I've double checked that "Figures require alternate text" is checked in the Alternate Text and Headings menu. Am I missing an option somewhere? I'm trying to create a workflow for my staff, and I'd much rather the error get marked correctly than to try and get them to remember to handle it.
If I take the same file that Acrobat passes, and then run it through another program, like the PDF Accessibility Checker, it correctly flags all of those images that Acrobat passes as images without alt text.
Do the figures have text in the Actual Text field instead of Alternate text? I have seen this pass the Acrobat XI checker but fail PAC 1.3 (surprisingly, it seems to pass PAC 2.0). The other thing I would check is the Content pane to make sure the figures are not hiding inside of artifact containers.
Thanks, a C student, that was indeed the issue.