How can I get PDFs to open in-browser in Safari 5.1 Basically the exact opposite of this existing question How do I disable inline PDFs in Safari 5.1?.  

I need to view my PDFs in-line, and with Safari 5.1 it's no longer working on either OSX 10.6 or 10.7.
If you install Adobe Reader when you open for the first time you will see this box, select yes.



If you already have it installed go to preferences and make sure "Display pdf in browser" is checked.