Well I already know that Paypal won't issue refunds for Digital goods, so I wanted to know how can you sort of "marking" your items as Digital good I mean, how does Paypal know that you are selling Digital goods? I ask this as a Seller, to avoid scams and so.
In order to sell goods and to have PayPal as payment processor (official) you must have merchant account. In the moment when you submit for merchant account for PayPal you'll have to complete some steps where you'll have to mention the goods that you're intending to sell as well. So this is how PayPal will know what you sell. If you don't do that, and you sell your "digital products" by using a normal account then the chargeback will be something very often because PayPal will not be able to protect you from these kinds of procedures that are so often.
You don't need to pay anything, just take a look on the PayPal account what papers you need to provide and signup for it - only if you consider that you're capable to provide them the papers, if not - don't do it until you're 100% ready. A failure on supplying them all the requested documents can go in suspending your account. So prepare yourself before you submit for merchant account for PayPal.