Docbook
You can find great documentation on Docbook here.
Convert Docbook XML to pdf
First you need to install dblatex, the tool we will use to accomplish this task. You can do so by executing
root# apt-get install dblatex
After the installation succeeded, simply execute the following to convert your Docbook XML file to PDF:
dblatex MyDocbookFile
This command should produce the file MyDocbookFile.pdf if everything works fine.