Sorry you're having issues, Gideon.
I just tried a PDF I'd created a couple of years ago and it seems fine. Only issue I noticed was that since it was a very old book, the margins weren't pristine so the DX didn't crop them. Still very readable.
I can go through the whole process a bit later (Opticbook --> software --> Acrobat 8 --> PDF --> DX) and see if there are any issues I can see. I use the same process that you do, scanning to .tiff and then using Acrobat to pull them in to a single PDF. Note, though, that I have Acrobat 8, not 9.
Edited to add: I usually scan in the 150 - 300 dpi range because that's what most OCR engines prefer. I don't remember offhand what dpi I scanned the above PDF in, but I would doubt if it was above 300.
Another edit to add: I usually scan B&W (not grayscale) unless it's an image like a photograph.
Last edited by Studio717; 06-17-2009 at 10:41 PM.