Solved this issue.
We were opening older versions of Adobe PDF's, which threw the error.
Going into Tools/Optimize/and change the compatibility setting.
Hopefully this can help others with the same error.
We are experiencing the same problem here - However, I did change the settings, but it did not correct the problem. We are all on the Cloud version of Adobe, so it's the latest update.
What version setting doe it need to be modified to?
What is the compatibility setting?