[geoschmo]

Acrobat has a text select tool, but you can configure the pdf when you create it so that the text select tool does not work. If outputting to txt is giving you a blank file then that probably means they have done this. It's a rudimentary copy protection feature for ebook publishers.

You could get a print to pdf driver, there are a few free ones out there, and "print" a few pages at a time of the original into smaller pdfs.

If nothing else works, you could zip the pdf and break it up into volumes. The downside to this of course is you won't be able to read any of it until you get all the parts at work and put back together. But it would get around the big file problem.