Apr 06, 2017 - 06:57 AM
This Adobe page details steps to download previous editions:
Hopefully that helps somewhat?
Apr 10, 2017 - 03:52 AM
Apr 10, 2017 - 04:20 AM
Looking into it a little further, there seems to be the ability to keep/re-install your previous Acrobat XI edition if it was uninstalled during a CC/Acrobat DC upgrade:
Which may help in certain cases. Otherwise I think Ian is right that Acrobat DC doesn't give downgrade rights.