Prestashop PDF Download Attribute - simple

I need an ADD-ON feature implemented to attributes on products. The website is built with Prestashop. The ADD-ON needs to allow the customer to pick between a book or PDF version. If it's a PDF, they get to download the product after paying otherwise it uses the normal checkout that uses shipping, taxes etc. Essentially they will just be paying for access to a downloadable file. There is already a attachment section for products so the connection shouldn't be too difficult.