Best Free PDF maker?

Hi, all. I'm sort of surprised to find myself in the Windoze forum, but that's how it goes I guess.

I'm getting fed up with people sending me documents that I only need to read in their Microsoft Office format. Usually, .doc and .xls are the culprits but today I received a .pub. A freakin' Publisher file! So, I'm instituting a new "idiot" reply for such folks, and I wanted to see what you Windows users are using for making PDF's. (It's built into OS X as it should be.)

There are only three requirements:

1. Free
2. Easy to download and install.
3. Simple to learn and use.

A quick search of VersionTracker didn't turn up anything with user ratings, so I am reticent to recommend any of them.