May 08, 2018 - 12:12 AM
As Ian said. Just one further point, in general the CC subscriptions include downgrade rights for the last perpetual version/edition of a suite product (e.g. Photoshop CC 2018 can be downgraded to Photoshop CS6).
This doesn't apply to Acrobat Standard (or Pro) DC though when purchased as a standalone subscription, or a perpetual license. However, if you've bought a Creative Cloud sub (which includes Acrobat) you could downgrade to a prior version of Acrobat.
As to the compliance risk, the anecdotal evidence is that Adobe aren't conducting audits - clearly the CC subscription revenue is satisfactory. Always best to remove old unused versions, if only because they won't be patched against ongoing security threats.