For user and admin docs, go to the directory doc/docbkx.
You'll need to install python Sphinx package and oslosphinx package:
sudo pip install sphinx oslosphinx
If you are using the virtualenv you'll need to install them in the virtualenv.
Just type make to get help:
make
It will list available build targets.
To build the man pages:
make man
To build the developer documentation as HTML:
make html
Type make for more formats.
If you modify doc files, you can type:
make doctest
to check whether the format has problem.