25 Pa. Stat. § 2874
Any of the candidates for nomination or election at any primary may withdraw his name as a candidate by a request in writing, signed by him and acknowledged before an officer empowered to administer oaths, and filed in the office in which his nomination petition was filed. Such withdrawals, to be effective, must be received in the office of the Secretary of the Commonwealth not later than 5 o'clock P.M. on the fifteenth day next succeeding the last day for filing nomination petitions in said office, and in the office of any county board of elections, not later than the ordinary closing hour of said office on the fifteenth day next succeeding the last day for filing nomination petitions in said office. No name so withdrawn shall be printed on the ballot or ballot labels. No candidate may withdraw any withdrawal notice already received and filed, and thereby reinstate his nomination petition.
25 P.S. § 2874