Please let us know your OS and version of Reader installed on your system.
Also, let us know if you have Acrobat installed on your system or not?
Adobe Reader 10.1.2
I do not have acrobat installed
"Display PDF in Browser" is greyed out in Adobe Reader 10.1.2. This is by design.
Also, There are known compatibility issues between Safari and Adobe Reader. Please see
the page also includes link to an plug-in on Adobe Labs that is under development.
You can try downloading the pdf on your computer and then open it with Adobe Reader desktop application
This is a continuing issue. I have the full Acrobat X Pro on 10.6.8 and the checkbox is checked, but greyed out, so I cannot uncheck it. That means that whatever browser I'm using always tries to view the PDF within the browser rather than downloading it. That would be fine, except I constantly get an error stating "Couldn't load plug-in".
Adobe needs to let me uncheck that box!