Kehn1950fx appears to have hit this one on the head... for some Portable Document Files.......

However, as has been said about .pdf conversion/testing/whatever -- in many threads here in the Monastery and elsewhere -- the standard for such docs has changed many times; many creators ignore or bork their implementation of the standards; and what you get may not match the output using a different source.

You may wish to check CAM::PDF and especially http://search.cpan.org/~cdolan/CAM-PDF-1.60/bin/getpdftext.pl if your desire to go further -- for example, to text extraction... but as the author, Chris Dolan http://search.cpan.org/~cdolan/ has noted (in paraphrase) extracting information from some .pdf formats is a real pain.