In order to use certain South-African documents in a country outside South-Africa, you may be required to have such documents legalised for use in that country. The rationale behind this is that individuals, organisations and government authorities want to know that a document or signature is authentic and when a document comes from another country, they may want an international certification.
This is where a notary public comes in. Notary publics have the authority to authenticate and witness documents and signatures on documents. Further steps in the legalisation process shall need to be carried out in order for the document to be used outside South-Africa.