Document submission to KIPO is possible either by fax or by mail.
Facsimile number is 82-42-481-8578. 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, 189 Cheongsa-ro, Seo-gu, Daejeon 35208 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.