Came back to reference this post and was surprised to see this marked as answered. The answers here are not satisfactory and the problem outlined in this post is not resolved. Under the guise of "updating" the Adobe CC app is designed to uninstall a licensed copy of Acrobat XI and install Acrobat DC even if the user isn't licensed to use that software. This eventually leads to the user being prompted to purchase Acrobat DC once the trial expires.
Maybe reply back with:
"Sorry we're greedy and we designed the program to force users off their old perpetual licenses."
I'd happily mark that answer as correct.