Business signage installation typically requires a Zoning Permit, but may only require Zoning review for most refaces (please note that dark lettering on light backgrounds is discouraged).
The sign chapter of the Planning Code is accessible online under OMC 17.104. Please be sure to review the Commercial Design Review Guidelines for commercial signage.
To determine your zone and to measure your parcel frontage to determine maximum signage per property, view the City's online Zoning Map. 20 sq ft per tenant is automatically allowed as a minimum; includes all commercial tenants.