Disclaimer: I've not used
xpdf in this mode, so I am speculating here.
Despite what it may sound like like at first reading, I don't think it is talking about an "over the network" type server. I think this is a way to start an instance (window) of
xpdf and then control the contents of that window (or shut the window down) from the command line (or script). I am guessing that only the user that started the "server" can control it.
If you would like to start an instance of
xpdf on a remote machine and view it on the local machine, then (just like any graphical application) you can (with proper authentication, etc):
Code:
ssh -X <optional user name@>remotehost xpdf document.pdf
Depending on configuration files, you may not need the
-X option.