I’m not entirely certain, but I think you are looking to use this plugin or one like it.
http://wordpress.org/plugins/easy-digital-downloads/
You should be able to create free download pages for no cost to your users.
Another option would be to just use a second page. In post option “Download Link” box, put the link of another WP page that you would create. Then on that page, have the actual download link formatted how you would want.
Cheers!