http://cpansearch.perl.org/src/CDOLAN/CAM-PDF-1.55/bin/changepagestring.pl

Use Data::Dumper to examine the output of getPageContent (or getPageContentTree

And the most important part, get the PDF manual, http://partners.adobe.com/public/developer/pdf/index_reference.html► http://www.adobe.com/devnet/pdf/pdf_reference.html