Note: This applies to DocuShare installations that will be connecting to SQL Server only.
If Database Owner is the User specified in the DocuShare configuration they would have full privilege to create/modify/delete all objects within the DocuShare Database which should be sufficient.
During DocuShare installations and/or upgrades a database admin account is needed to create the database, temp tables, etc, but other than installations and/or upgrades the DocuShare user account does not need any special roles providing they are the Database Owner.
Warning: Development recommends the DocuShare user have System Administrators role since those are the roles used during product test. Please test any other user role the customer may want for the DocuShare user in a test environment prior to rolling it to production.