Looking for file download / account manager plugin

I’m not sure where to post this. This seemed like the most logical spot. Please help!

I’m building a corporate site for a client on WordPress. As part of the site, there’s a traditional-looking blog. One of the categories of the blog will be for special research documents that they write. These will be published as an attachement to a post that sums up the research.

Requirements for the research section include:
1: Readers can see and read the entire site including the special “research” category

2: To download a file from within the research category, users would have to fill out a short form (name, email, company, job title, etc.) and create an account with a un/pw

3: Users who have previously downloaded a file would not have to go through the hassle of doing the form the next time the come back (the get cookied somehow).

I haven’t been able to find a WP plugin that will handle this. Does anyone have an suggestions? Or can someone propose a possible solution?

Thanks!
.g