Actually a volume license is not a prerequisite.
Follow the link provided in the first answer.
Select Acrobat XI Standard or Pro.
Both have the same EULA.
This link takes you to the PDF:
This section addresses "Portable or Home Computer Use" and speaks to install of a second copy of the Software for the specific user ("Primary User") usage on a portable computer or a computer located at home.
This would cover a license for the software that an individual purchases.