+jack wallen of Linux.com posted an article on PDF Chain. This is the first I have heard of it, but I guess it adds a GUI to PDF Toolkit.
PDF Chain consists of four tabs; catenate, burst, background, attachement, and tools. Catenate allows to to stitch or add several PDF files into one. Burst allows you to take a PDF and burst it into single pages. Background more or less allows you to add a watermark. Attachement is self explanatory and tools adds compression.
One of the nicer aspects of this app is the ability to encrypt and password protect the PDF. You can set owner and user passwords, as well as, control access to printing, copying, modifying, annotations etc...
In the video burst a 20 page PDF, and then stitch three of those pages into a new PDF. I was pretty impressed with this app, although it is not one I would use regularly.