When configuring Adobe Reader XI to disable “Display PDF in Browser” you Adobe released ADM and ADMX files, but they didn’t worked for me. You can download them here: Adobe Reader XI ADM(X)Templates.
Whe opening Adobe Reader and you like to disable “Display PDF in Browser”, you are redirected to a website to manage Internet Explorer Add-ons, I use the Group Policy to control the environment and manage my Add-ons using the Add-on management. Open GPMC and edit the apropiot policy, go to User Configuration\Policies\Administrative Templates\Windows Components\Internet Explorer\Security Features\Add-on Management there open the Add-on List.
Name: Adobe PDF Reader
Publisher: Adobe Systems, Incorporated
Class ID: {CA8A9780-280D-11CF-A24D-444553540000}
I always copy the above settings to the Comments field so someone else can see where the Class ID is from.
Enable the setting and select Show. Then use the following Class ID for Adobe Reader XI:
Value name: {CA8A9780-280D-11CF-A24D-444553540000}
Value: 0 (zero) (to disable the Add-on)
Click on OK and again click on OK. Now close the GPO and login as user, the PDF will open with Adobe Reader and not within the browser.