To using Safari 2.0 to open PDF, my experience is with Preview is faster that Acrobat, less buttons to load in the browser .
But when you have installed Acrobat into your MAC, it became the default and kick out Preview from Safari. There is a way to stop Acrobat.
Run “Acrobat”
Go to “Preferences” like this window
In “Internet” option, unchecked “Display PDF in browser using:”
Click “OK”.
Ah~ Now it is much better! :P