Can anybody help?

Selling PDFs online and I've been going about means of distributing and preventing them being duplicated.

Id like to create a user domain on my site, so the user can enter an email address of their own & password which takes them to their own page. And once they've paid for the pdf's they can only access it through this method...

Does anybody know how I go about setting this up? Any advice is much appreciated as TG has been extremely helpful to me recently, what with being a new developer & user of Xara.

Cheers
James