53 Pa. Stat. § 7188
Any claim, petition, answer, replication, scire facias, affidavit of defense, or other paper filed of record, may be amended, from time to time, by agreement of the parties, or by leave of the court upon petition for that purpose, under oath or affirmation, setting forth the amendment desired, that the averments therein contained are true in fact, and that by mistake they were omitted from or wrongfully stated in the particulars as to which amendment is desired. Such amendments shall be of right, saving intervening rights, except that no amendment of the claim shall be allowed, after the time for its filing has expired, which undertakes to substitute an entirely different property from that originally described in the claim, but the description of the property may be amended so as to be made more accurate, as in other cases of amendment.
The court may, for cause shown and filed of record, enlarge the time for filing the affidavit of defense, answer or replication, for issuing a scire facias or for entering security, by rule or special or standing order; and any judgment by default may be opened by the court, upon cause shown by intervenors or other defendants, as in other cases; but no enlargement of the time for issuing a scire facias shall extend the same beyond the time herein provided for preserving or retaining the lien thereof.
53 P.S. § 7188