in reply to exporting PDF::API2
(You can find the script utilized in my blog)
So the problem here is not that your pdf can't be copied (or opened to read). To lose the select/copy text ability is a common trouble when a pdf is repaired/fixed with some programs.
In short: a pdf can be optimized if you convert it again to ps, and then you use ghostscript (or ps2pdf) to recreate it. You obtain a smaller archive but you can lose more modern features and things like text selection, (typically in the first pass). The cause avoiding you to select a text can be, i.e., in the encoded fonts utilized.
You can fix this with Adobe software (or probably messing with the inner structure). Take a look to the documentation section of the CAM-PDF module from Chris Dolan with a lot of useful (and better) perl scripts to analize your pdf