Paynester

Site URL: https://inverroy.squarespace.com/ Hi All, Apologies if this isn't in the correct area but I couldn't see where to put it. I am trying to add a button that allows people to get a free digital download but only if they enter their email address first. I could do it under commerce and make the product free but they have to enter their full postal address for that and I'm pretty sure we'll lose people as a result. Other web sites I've seen let you click the link to the download and take you to a pop-up that requires your email address to continue which is what I want. Any ideas please? Thanks in advance, Paynester