72 Pa. Stat. § 7245
Any person maintaining a place of business within this Commonwealth is deemed to have appointed the Secretary of the Commonwealth his agent for the acceptance of service of process or notice in any proceedings for the enforcement of the civil provisions of this article, and any service made upon the Secretary of the Commonwealth as such agent shall be of the same legal force and validity as if such service had been personally made upon such person. Where service cannot be made upon such person in the manner provided by other laws of this Commonwealth relating to service of process, service may be made upon the Secretary of the Commonwealth and, in such case, a copy of the process or notice shall also be personally served upon any agent or representative of such person who may be found within this Commonwealth, or where no such agent or representative may be found a copy of the process or notice shall forthwith be sent by registered mail to such person at the last known address of his principal place of business, home office or residence.
72 P.S. § 7245