At this time you can select Paper billing to receive your invoices monthly and your current invoice will be available online via My Account (only as a summary). With ebilling you can review up to 24 months of invoices online and fully access them.
Unfortunately both options are not available at this time, though I always recommend ebilling as My Account tracks the invoices for you so you don't have to worry about sorting and files, and can just review the invoice and close the window without wasting paper or having to deal with the post. If you do wish to have a copy of the invoice, you can print it off your printer.
PDF files should work on any computer as PDF's use Adobe reader which is normally installed by default. If not you should be able to download it for free from the Adobe reader website.