Sounds like the PDF has been password protected to guard against specifically what you're trying to do. I've encountered this many times and still haven't found a solution.
I couldn't find any reference to either of the two previous commands in the 10.2 install. is this something that's available elsewhere?
This solution may not be the best for you but I had an app that came with my scanner (only <=OS9) that could scan directly to PDF... a cool functionality of it was it could load a PDF and use OCR on it. It created a text document of the text in the PDF.
For OS X I have seen a util that will allow you to copy text out of protected PDF's but I can't remember where it came from or what it's name was.