To issue an official certificate (E.g. Certificate of Enrollment, Certificate of Graduation, Academic Transcript, etc.), please refer to the following website of One-Stop Service Center. kucert.korea.ac.kr
You can either print the certificate yourself or send it directly to institutions. 
*PDF download is not available. 

For those who need a certificate not issuable at the One-Stop Service Center, request it to gsis@korea.ac.kr.