Sorry ... must ... say ... it ...
Use OS X sinnce it creates, reads and edits PDFs natively (PDF is actually part of the display model).
Says something about the Win OSes that handling PDFs becomes such a big deal.
If you use Firefox on Mac OS X, be sure to install the Firefox PDF Plugin for Mac OS, by Sam Gross. It shows the PDF right in the browser, using the same PDF support built into OS X that the Apple-supplied Preview app uses. I use Preview to look at PDFs on disk. There is no need to install Acrobat Reader on the Mac.
On Windows, I use the Foxit Reader. No need for Acrobat on Windows, either. It's a bloated mess. It also contains security holes — open the wrong document and you are owned!