Freeform: how to make a download document form sending the document url ?

Hello all,

I would like to create download forms for entries in a specific weblog. The idea is that, on the detail page, the visitor gets a summary of the document and a short form (name, surname, email). Upon form submission, a mail is sent to the submitted email address, giving him the exact URL to download the document (and the submitted data are strored in a database).

I believe I have to use the Freeform Module but I cannot figure out how to sent out an {exp:weblog:entries} value (the URL of the doc) to the user. I have been searching how to do that but cannot come up with a working solution. Any help (inluding other solutions) will be appreciated.

Here is the functionality I am trying to replicate.