Documents that are issued in one country (your country) which need to be used in another country (Korea) must be authenticated or legalized before they can be recognized as valid in the foreign country (Korea).
Documents that need to be authenticated with an apostille:
Both documents should be authenticated with an apostille seal certificate. However, Canadians are required to secure a Korean Consulate verification stamp as an alternative to the Apostille authentication. American, British, Irish, South African, Australian and New Zealand citizens are all required to use their respective Apostille issuing office
Click on your flag for more specific information on getting an Apostille authentication: