Q: creating good-quality PDFs from scans?

[D. R. Evans]

I've installed gscan2pdf, and when I try to use it I get the remarkably
unhelpful:
  Unknown message: scanimage: attempted to set inactive option threshold

Googling around, I can't even find out what the message means, never mind
how to fix it. Does anyone have any idea what's wrong?

As I mentioned before, kooka works fine, at least insofar as obtaining an
image from the scanner is concerned.

  Doc