Notarizing a Signature By Mark in Pennsylvania
RULONA does not have specific statutes in place for notarizing a signature by mark, however, PAN suggests having two witnesses present for notarizations where the signer is signing by mark. This helps to protect not only the notary, but the customer, from any claims of fraud.
Both witnesses should be noted on not only the document, but in your notary journal. A properly witnessed mark is considered a valid signature, so no additional notary certificate is required.