If you're a heavy user of the GNU/Linux command line, then you're already familiar with the man command. If you're a newbie, the man command (short for manual, as in RTFM) pulls up the online documentation for terminal commands and outputs it to the same terminal. Perhaps you wish you could have some of these handy documents loaded on your PDA or smartphone as a reference.
If I wanted to know how to call up GNOME's document viewer, Evince, I could open a terminal and type:
With the following simple command you can get a man page to output as a PDF. Then you can copy it to your device of choice for portability. (I'll use evince again since it has a short man page.)
Now I can view the new pdf with
Here's what the resulting pdf looks like: Evince Man Page