I wan't to open a pdf. If I go to Windows Explorer, I'll see a thumbnail with the first page of the pdf document. This is also visible in Outlook.
If I want to open de document, Adobe Acrobat Pro XI doesn't start.
Adobe Acrobat is set as the standard application which opens the pdf files.
Why do I see the thumbnails but doesn't open?
As mentioned above you are facing issue when trying to view a pdf file using Acrobat XI, could you try the troubleshooting steps mentioned below:
1- Reboot the machine once if you haven't already and check.
2- If that doesn't work, check if an update is available for Acrobat using "Check for updates" option under "Help" menu, reboot the machine after installing update and try again.
3- Launch Acrobat as an administrator- Run an Adobe program as administrator | Windows 7, Vista
4- If issue still persists, try the troubleshooting steps given in the following help document: Can't open PDF
Also, let us know dot version of Acrobat and the operating system installed on the machine? You may refer to the steps given in this link on how to check the version in Acrobat: Identify the product and its version for Acrobat and Reader DC
Let us know if you need any help.