kbdrate's very well-laid out PDF version of the QuakeC Progs 1.06 source code is in the downloads section under source codes.

If printed it is only 127 pages long.

If you need to browse the QuakeC online, Inside3d has an excellent online progs 106 browser at Link deleted. Site has apparently been hacked or it redirects to a hacked website. (Canadian*Sniper)

That being said, having a printed version for reference is indispensible if you are going to be heavily into QuakeC as there some instances where a printed copy is more useful and other instances where browsing it online is more helpful.

Download location: Downloads -> Source Codes