Recently I've been using various pdf tools to watermark pdf's and generally play about with them. They are
from https://github.com/sjau/pdfForts and have various tools, like -
This script adds a password to the PDFs.
Lets you edit the current bookmarks and apply them to the PDF.
Combine PDFs and maintain bookmarks.
This script lets you extract one or more pages from PDF.
This script lets you extract text from a PDF.
Add meta data to a PDF.
This script converts image PDFs to text files using tesseract.
This script creates a copy of a PDF without password. The password must be known.
Rotate a PDF by 90°, 180°, 270° clockwise.
This script just adds a document number and page number on a bunch of selected pdfs.
Lets you add a watermark across the PDF.
As this is from a git repository you need the following commands to get them, and to keep them updated -
git clone git://github.com/sjau/pdfForts
and to update -
git pull origin master
They all require you to use linux, with its various distributions of your choice, and to use KDE as your desktop environment, or have it installed. I use GNOME but do have KDE installed and use some of its programmes. They are in active development so you need to update occasionally.