I just installed Real FLight 7, Remote Control FLight simulation software. Whenever I try to open a help file, I get the following message:
KEEror 21086: Error opening manual c:\program files (x86)\realflight7\documentation\english\realflight 7 manual.pdf error code 31

Make sure you have installed an application like Adobe Reader that is capable of viewing .pdf files.
(omit junk about adobe installer on the installation media)

Adobe Reader is installed, and I can go to the above location and open the files directly. The vendor had me create another user and run the software from that user, and it opens the help file fine. At that point they're pointing a finger at Windows and refuse to help further.

Windows 7 Pro x64, up to date. HP i5, 8G memory.

I think KEError stands for "Knife Edge Error", where Knife Edge is the software author vendor.
Any suggestions greatly appreciated.