Can a Pennsylvania landlord raise rent more than once a year?

It depends on the tenancy type and any applicable rent control. On a month-to-month tenancy, a Pennsylvania landlord can technically issue multiple rent increases in one year, each with the proper notice (Pennsylvania uses 68 P.S. 250.501 tenure-based notice: 15 days for tenancies under 1 year, 30 days for 1 year or more. No state rent cap. Rent changes on month-to-month tenancies follow the same notice ladder.). However, in jurisdictions with rent caps (California's AB 1482, Washington's HB 1217, New York's Good Cause coverage), the annual cap applies regardless of how many increase notices are issued. So even if a landlord delivers two increase notices in 12 months, the combined increase cannot exceed the statutory annual cap. On a fixed-term lease, no increase is permitted during the term unless the lease itself authorizes it, regardless of state. After the term ends, the landlord can issue an increase as part of the renewal offer.

Source: 68 P.S. 250.501 (Pennsylvania Landlord and Tenant Act 1951)