I seem to have a problem with Firefox's builtin PDF viewer. Instead of black text on a white or gray background or something else sensible, I get black text floating over my desktop background in the part of the Firefox window that's showing a PDF. PDFs display fine in an external viewer, but that's just passing the buck, isn't it? Is there a way to fix this on Firefox?

I suspect hardware acceleration is the issue, but everything else seems fine, so I don't want to just blanket disable hardware acceleration. How can acceleration for PDFs alone be disabled?