download product

the user is unable to see the link to the product, however once the product has downloaded the link is exposed.
is there a way to hide the link? or to download from temp folder then delete it?

Not sure that I got you. Please clarify.

P.S. If you want to limit a number of allowed downloads, go to a product variant details page, uncheck 'Unlimited download' under 'Downloadable product' and set maximum number of allowed downloads to 1. Is it what you're looking for?

Lets say i have a product to download at www.store.com/product.rar
once the user paid and downloaded the file, the link above is being exposed.
the user can publish the link for others and they can download the file directly.

Not out of the box. It needs some coding.

may be for the next version, copy the file to a temp folder and then delete it for every download

This is part of what I was questioning within my post to the community in the following post:

https://www.nopcommerce.com/boards/t/13080/best-practice-for-downloadable-products.aspx

In short, it would be nice to secure/manage downloadable content in a similar way customer's invoices(on file system) are currently secured/managed.