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 command-line tool for doing everyday things
with PDF documents. Keep one in the top drawer of your desktop and
use it to: Merge PDF documents, split PDF documents, apply watermark,
repair corrupt PDF, update PDF metadata and much more.
pdftk does not require Acrobat and is free software (GPL)

pdftk requires java.
