You can link directly to your digital download here. Be sure to link directly to the PDF/Doc/XLS/etc. DO NOT link to your email signup page - this is NOT about building your list, this is about giving tons of value without expectation.
And if someone bothers to read your download, they will probably be more committed to finding out more about you, your products and services.
So give first.
And link only to digital content that you own the copyright to. If it’s someone else’s content, make sure you have permission to do so.