I don't know what plan you are on, but unless you have absolutely thousands of customers downloading each month, I think the bandwidth consumption would be trivial.
As I think you already suspect, that's a "how long is a piece of string?" question. All you really need is:
- A folder for the PDFs that is protected from the outside world by .htaccess
- A database file with 3 tables (users, files, and a join table of both)
- An admin panel that allows you to grant or deny password holders access to files
- A web page that displays links to all the files accessible by a particular user (which may be one or more patterns, presumably) - sort of like a digital locker
Something like that is 2 or 3 hours of work, I would imagine, unless someone has a pre-built package that does the job. Probably somewhere in the region of $100-300, maybe? I normally design whole websites (rather than little bits, as it were), so it's a little hard to estimate. Someone here might be up for doing it for fun if you're lucky!
Simon Jessey | Keystone Websites
Save $97 on yearly plans with promo code [color=#CC0000][b]SCJESSEY97[/b][/color]