Ah, the PDF file. Like it or not (and there are many standing on both sides of that line), the PDF has somehow, in some way, become ubiquitous. It's become a de-facto standard document file format.
Nowadays, a range of different applications and tools can spit out PDFs with the click of a button or an option added to a command line. Generating a PDF is one thing. Manipulating one is something else. On the Linux desktop, there are several utilities which can do just that. Let's take a look at two of them.