Document submission to KIPO is possible either by fax or by mail.
Facsimile number is 82-42-472-7140. You need to press 011 if dialing from the United States.
Mailing address is as follows:
International Application Division Korean Intellectual Property Office Government Complex-Daejeon, 139 Seonsa-ro, Seo-gu, Daejeon 302-701 Republic of Korea.
Please bear in mind that it can take about a week for mail delivery. Your mail should arrive at KIPO within the due date.