Dealing with returning subscribers

Most of my site is free content at this point. I have a lot of free pdf and files that I am trying to add to my site, mostly links inside blog posts so that the files can be downloaded. I am trying to figure out if there is a way to check the email address against a current list and send a separate email if they are a current subscriber to my lists? I am trying to keep from having people getting a bunch of welcome messages. I am new so maybe I am missing a setting but can I link to lets say a pdf file and have the person enter their email address and only send the file to that address to verify the address, or send the email with a link to download the files?

I hope I am just missing something easy or if anyone can explain a better way to get files to people without missing them on my mailing list.