Adobe Acrobat 7 Professional - Manual (Page 30)

If you want to view an Adobe PDF document on the web
PDF documents can be opened either in Acrobat or in a web browser.
In Windows, you may need to configure your web browser to open PDF documents. In
Acrobat, open the Internet panel of the Preferences dialog box. Select the Check Browser
Settings When Starting Acrobat option. Also, make sure that Display PDF In Browser is
selected. Then restart Acrobat. If this procedure doesn't work, you may need to update
your web browser.
Mac OS automatically configures Acrobat to run in the browser (Safari) the first time you
start Acrobat after installation. (See
Viewing Adobe PDF documents in a web browser .)