I've got a PDF in progress using LaTeX, and I'm working on learning Scribus so I can make a more fancy version (LaTeX is primarily intended for writing technical articles; it can do tables, figures, automatic numbering, any sort of math you can imagine, and it will automatically flow text around these, but it's not much good for fancy things like cool sidebar or page formats; Scribus is a proper desktop publishing application, so it will let me make a document that actually looks like a proper game rulebook). You all will be the first ones to hear about it when it's done!
FYI, the 2010 (2011? 2012?) PDF is at 206 pages, and we still have 3 chapters to go...
Heuristic ALgorithmic AFOL.
T6281: Solar Federation (Rules T6588)
T6777: Dungan Swarm
T6783: Space Pirates
T7349: BrikWars Vehicle Datasheet
T7402: Imperium Constructor