I have created alt-text for all my pictures in Adobe Bridge. I placed them in InDesign, and do see the alt-text from within InDesign
Object / Object Export Options / Alt-Text / source: from XMP: Description
I do see the alt-text I entered in Bridge.
When I export the file to accessible PDF, however, it says there is no alt-text.
What am I doing wrong?
I'm guessing that when you exported from InDesign, you may have forgotten to check Create Tagged PDF in the Export PDF dialog.
I just tested with a small file I had that has metadata using InDesign CS6. I selected the Alt Text option in Object Export Options as you did:
I turned on Created Tagged PDF when I exported (works with either PDF (Print) or PDF (Interactive). When I opened the PDF in Acrobat, if I paused over the image with the Hand tool, I could see a tooltip (indicating the Alt text).
Or, you can choose the Edit Object tool (Content panel) and select the image. Then right-click on it and select Properties. You'll see it under the Tag tab: