default PDF reader on a Mac is Preview.
It is possible that the Adobe plugin is not working correctly, a problem with Adobe and Lion.
Try this
Quit Safari.
Open the hard drive and go to Library > Internet Plug-Ins and remove ALL Adobe, Acrobat and pdf plugins that you find.
Repeat with your Home > Library > Internet Plug-Ins.
Launch Safari and see if that makes any difference
let us know
P
When I click on a link a blank page opens and then nothing downloads. I am using Lion, the latest Firefox and Adobe Reader on a MacBook Pro.

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