slackbuilds/office/pdftk/README

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 watermarks,
repair corrupt PDF, update PDF metadata, and more.  pdftk does not
require Acrobat and is free software.

NOTE: Starting with Slackware 15.0, pdftk compilation requires SBo
gcc-5 because gcc-java was dropped from the GNU Compiler Collection
as of gcc-7. Don't forget to source /etc/profile.d/gcc5.sh before
starting to build this, like:

  . /etc/profile.d/gcc5.sh