PDF attachments from application is not opening correctly. Adobe Reader spits this error message.
We use RDS 2012 R2 and Profile Disks for the users. Somehow PDF files on the profile disk is having same issue with Adobe Reader.
Solution: It turn out to be new Adobe Reader software has Protected Mode feature. This feature has issues with Profile Disks and Roaming profiles. Just disable Protected Mode under Security (Enhanced) section in Preferences.
Hope this helped you. Leave me a reply. 
Thank you for this Post. Turning off Protected Mode is no option for us, we have it enabled for security reasons.
In our enviroment we have redirected the desktop to a Network Share. When opening a PDF from the desktop, we recieve the same “Access Denied” message as you.
Surprisingly the PDF opens correctly if you delete the desktop.ini file from the desktop.
This behaviour doesn’t make any sense to me, and it’s also an insufficent workaround, but maybe it helps someone to find an ultimate solution for the problem.
Is there a solution to do this for all users? As far as I can tell every user needs to deselect the checkbox. In a large environment this is a problem. Anyone has a solution for this checkbox?
We have both scenarios:
1. RDS 2012R2/Profile Disk
2. RDS 2012R2/Redirected profiles to fileshare.
We need to go to profile disks but I can’t because than I have problems with Adobe pdf files and printing issues. To solve that is to disable Adobe Protected Mode but not for us because it is a good security thing to have it on. It is also recommended by Adobe.
Hope someone have a solution.
Hi ALL!
How to disable it via GPO ????
For Reader DC add GPO
User Configuration\Preferences\registry
HKLM\SOFTWARE\Wow6432Node\Policies\Adobe\Acrobat Reader\DC\FeatureLockDown
bProtectedMode = 0x00000000
but why Wow6432Node ???
We have this issue in 2008 R2, Adobe Reader DC. Protected mode is turned off and we are using roaming profiles. We have yet to fix our issues, any other ideas?