One of the things I like about being in the technology field? All the emails offering "free" tech reports, whitepapers and the like. Then, you click on the link to said "free" report, and you're greeted with a damned "please register" page.
I don't understand the motivation. You're marketing these papers towards technical folks. In other words, you're setting up login barriers to the people least likely to give you their real contact information. Sure, I'll register and give you an email address and a phone number, but precisely 10 minutes after I receive the "here's your login information" email, all the requested contact information will cease to exist. So, what was the point?
The funny part is when the toolbags that "offer" these documents are simply putting a registration banner in front of something that they downloaded from somewhere else. It seems they forget that: A) Google (et. al.) exist; and that, B) the document they're offering was originally available from a site that either had no registration requirement or one that was significantly less time-consuming to get through.
And, as a final note: taking what was previously published as an HTML document and providing it as a PDF doesn't make it worth me downloading it from your site and giving you my (fake) information. I've got a "print to PDF" tool installed (if you run Linux, OS•X or even a more recent Windows iteration, it's part of the OS) on my laptop. In other words, I get no benefit from downloading it specifically from you.
Lastly, if your registration process is too involved, such that it takes me less time to Google an alternate source than it does to get through your gateway, guess what I'm going to do. I'm big into instant gratification. Why the hell would I jump through hoops and waste time with your site?