Well, free and not-for-free, I use WebSuperGoo ABCpdf .NET component, that I just love it!
not-for-free because you need to pay for it.
for free because even if you have to pay, they have a trial version and you can request a free license if you do not mind that, in your site show "This site uses WebSuperGoo ABCpdf .NET component" with a link to their website.
I did that and I got a free license (version 5 in that time) so, I can say that it works (even if the website is no longer online) - I still have and use the component ~:)
A wonderful thing that I love with this is that you can do everything that you can thing off with this, create PDF forms and dynamically fill them and send to user by mail or have them to download it, create a pdf from scratch, convert HTML pages into PDF, etc etc etc, please read the documentation, it is a wonderful component.