"If PDF is electronic paper, then pdftk is an electronic staple-remover, hole-punch, binder, secret-decoder-ring, and X-Ray-glasses. Pdftk is a simple tool for doing everyday things with PDF documents."

This is a <img src=/S/free.gif border=0 alt=free width=30 height=15> (GPL) commandline tool with lots of features for PDF manipulation. Looks neat - about to try it now.