S.C. Code Ann. § 30-11-30: Proof of execution of written instruments.

Before any such deed, lease, mortgage or other instrument in writing can be filed by the Secretary of State, the execution thereof shall first be proved by the affidavit in writing of a subscribing witness to such instrument, in the same manner prescribed for the probate of deeds in relation to the recording of deeds in the office of the register of deeds of the several counties of this State.