1 Pa. Code § 33.32
Pleadings, submittals, briefs and other documents, filed in proceedings pending before an agency, when filed or tendered to the agency for filing, shall be served upon all participants in the proceeding. The service shall be made by delivering in person or by mailing, properly addressed with postage prepaid, the requisite number of copies to each participant as provided in § 33.37 (relating to number of copies).
1 Pa. Code § 33.32
This section cited in 1 Pa. Code § 33.36 (relating to form of certificate of service); 1 Pa. Code § 35.31 (relating to notice and action on petitions to intervene); 4 Pa. Code §607a.7 (relating to answer to order to show cause); 16 Pa. Code §42.34 (relating to motions); 25 Pa. Code §1021.34 (relating to service by a party); 25 Pa. Code §1021.91 (relating to general); 34 Pa. Code §111.12 (relating to filing, service and proof of service); 34 Pa. Code §111.14 (relating to motions to quash); 34 Pa. Code §131.11 (relating to filing, service and proof of service); 34 Pa. Code §121.34 (relating to objections to assessments); 34 Pa. Code §131.32 (relating to petitions except petitions for joinder and challenge proceedings); 34 Pa. Code §131.56a (relating to withdrawal of appearance); 37 Pa. Code §171.25 (relating to service); 37 Pa. Code §197.5 (relating to service on other parties); 37 Pa. Code §197.34 (relating to notice of appeal); 40 Pa. Code §15.44 (relating to service); 40 Pa. Code §17.13 (relating to protests/intervention procedure); 52 Pa. Code §1.54 (relating to service by a party); 52 Pa. Code §1001.52 (relating to service by a party); 55 Pa. Code §41.23 (relating to proof of service); 55 Pa. Code §41.24 (relating to certificate of service); 61 Pa. Code §703.5 (relating to other submissions); 61 Pa. Code §703.6 (relating to service); and 67 Pa. Code §491.8 (relating to service).