Hi Mike ,
There is no such policy to upgrade license from Acrobat XI Standard to Acrobat XI Pro.
If you have the subscription for the Standard version ,you need to get that cancelled and get a new subscription for Acrobat Pro.
If you have the retail version or if you have purchased the software ,you can return that and get a new retail version for Acrobat XI Pro.
For more information ,please contact the technical support.
Regards
Sukrit Dhingra