Some users of Adobe Acrobat Reader 11 may encounter an error when they attempt to open a PDF file from their email client such as Microsoft Outlook. An error may appear that says “There was an error opening this document. Access denied.” There is a simple fix for the error. Just follow the below steps.
From Acrobat Reader, select “Edit” > “Preferences“.
Select “Security (Enhanced)” on the left pane.
Uncheck the “Enable Protected Mode at startup” box.
Select “Yes” to the prompt about being sure about making this change.
You should be good to go! Adobe Reader 11 should now open files just fine.
Note: this is a per user setting. To take care of it for all users, there's an option of creating a GPO with the following registry change:
[HKEY_CURRENT_USER\Software\Adobe\Acrobat Reader\10.0\Privileged] "bProtectedMode"=(0 = off; 1 = on)
In the Acrobat Reader version make sure you have the correct version for the path. You would have the bProtectedMode to be 0.