so i don't have control over which modules can be installed.

Simply create a folder on your server and place your module in that folder. You then refer your script to that folder:

use lib '/home/users/my_site.com/lib';

use HTML::blah;
[download]

NB. So this would be a file called blah.pm inside a folder called 'HTML' inside a folder called 'lib'.

As for the main problem I was wondering if you might create a PDF file with your nicely formatted data, then invite the user to print that. I've never done it but there's quite a bit of stuff for PDF on CPAN which might help your cause.