Upgrade Acrobat XI Standard to DC Pro (how/cost)?

I bought a ScanSnap scanner that came with a copy of Acrobat XI Standard.  If I want to "upgrade" that to DC Pro, how would I go about doing that, and how much would it cost?

I assume less than a full new copy of DC Pro ($450)?  I'd like to purchase outright, not rent month to month.  I can't find "upgrade" prices anywhere on the "plans and pricing" page.

Thanks.