need user to complete a form to access certain content

I have a client who would like his users to be able to see most of his website just as the public does, with no data required from the user. But, within one particular section, where he has a dozen or so whitepapers published, he would like the user to have to submit name, email, phone, etc. in a short form before they can access the content.

I’ve tried dozens of plugins, but I can’t seem to find anything that does this task specifically. There are plenty of plugins that will email the user the content after filling out a form, but the ones i’ve seen perform this task one at a time on each piece of content. So for a dozen whitepapers, the user would have to complete the form twelve times. That’s not practical.

What I really need is a way to “unlock” certain pieces of content once a form is filled out once by the user.

Has anyone ever done something similar that would be willing to share the details with me? Thanks in advance.