scripting default PDF application

[Matt Law]

Hello!

I need to set XPDF to be the default PDF application on dozens of Fedora 
core 1 and core 2 machines.

I would like to write a shell script that installs xpdf if it isn't 
already installed and then makes it the default application for PDF 
files.  Can someone please tell me which file(s) control the default 
application behaviour in Fedora core 1 and 2?

Many thanks in advance,

Matt.