jonradio on "Email before download"

I am using WordPress 4.6 and I want to set up an email before download feature on my site. I want the user to be able to see all the content I have available to download and when they click download they get prompted to put in their email address.

Does anyone have any suggestions for me?

Not something that I have done, but your best approach is some careful searching of the Plugin Directory, and possibly the Theme Directory.

The only plugin that looked promising in my quick search was:
https://wordpress.org/plugins/sell-media/

You would have to see if it allows you to set a price of zero and not force payment.

Much to my surprise, this search is really promising:
https://wordpress.org/plugins/search.php?q=email+before+download

Among others, it turned up this popular plugin:
https://wordpress.org/plugins/email-before-download/