Forms have their own accessibility issues, but they are very
similar to those of an image; basically they need a text equivalent so that
they can be read by the screen reader. If you are interested in a large-scale
solution for massive paper-to-electronic conversion, the
Adobe Acrobat Capture plug-in
can be purchased from their site.
The next page offers a lab where you will be making an accessible PDF form from one that has no structure.