You can use E-junkie to sell any kind of digital product, tangible product, or intangible product or service.
If you have entered a Common Thank-you Page URL in your Account Preferences, we will direct all your buyers to that page after checkout regardless of the item(s) they purchased. PayPal will not auto-redirect buyers; they only provide a "Complete Purchase" button the buyer must click to proceed.
While you can set up a product-specific Redirection URL, that would not override your Common Thank-you Page URL, so the buyer would only access that product's Redirection URL via a link we provide, in much the same way as we provide download links. Product-specific Redirection is typically used to grant access to premium content, such as a pay-to-view article or video, or a secret "members only" area of a site.
You may be interested in using the method explained here to embed your E-junkie-generated thank-you page content (including download and redirection links) inside your site's Common Thank-you Page:
Then you might consider making the rest of your site's thank-you page suitably generic to be applicable to any purchase, and only adding special download instructions to those products' Message (HTML) fields in Seller Admin, so those instructions would only be displayed when the relevant products are purchased.