While rummaging around looking at the available options, has anyone come across anything that would be suited to just selling PDFs (i.e. no need for tax/delivery)?
And also, does anyone have any ideas how to impliment such a thing? Would you have a success re-direct to a specific URL or just to the PDF itself?

Can't help with the mechanics of how to deliver...But I've read many sales pages --you know, the ones that scroll down forever and ever, that say they'll teach you how to market your ideas. When you are selling pdf's, that's what you're doing- selling ideas, or selling information. So use those two phrases to start a google search and see what you can come up with.
There are site packages out there that are set up to sell digital documents. But I can't remember any names.

If you want to look into going the PayPal route, check out their website for info, something like Merchant Solutions or Website Solutions, especially their "Website Payments Standard". They have some extensive documentation how to implement it on your site, which they distribute as downloadable ... PDFs!