How do I get some documents notarized in Korea for use in my home country?

For notarization, you go to a notary public office, which are authorized law offices found in most city centers, and they can notarize documents, translations, and powers of attorney. Bring the document, your ID (passport or ARC), and for a translation often the original plus the translated version, and they affix a notarial certificate for a fee. For use abroad, Korea is part of the Apostille Convention, so for member countries you get an apostille rather than full consular legalization. Apostilles in Korea are issued by the Ministry of Foreign Affairs and, for certain document types, the Ministry of Justice; the practical places are the MOFA consular service or the government document service center in Seoul. The usual flow is to get the original public document (or a notarized document), then have MOFA or MOJ attach the apostille. If your destination country is not in the Apostille Convention, you instead need authentication by MOFA and then your country's embassy in Korea. Check whether your destination accepts apostilles to know which path applies.