This tutorial will be useful if you are trying to open file from SharePoint and getting this message,
Install adobe Acrobat extension on the web browser (user can install by themselves - no IT Help require) Click here to install
Once you have extension, the file will open in adobe browser version
Click on "Open On Desktop" and it will open adobe reader and the file will be readable.
If your computer do not have pdf reader please send ticket to [email protected]