If a document is issued by a certain country and it needs to be used in another country, it requires authentication to be able to be considered valid to present in another country. An Apostille Document undergo a certain process where different seals are placed on it. Documents that needs this kind of authentication are power of attorney, certificate of birth, death certificate and marriage contracts, business papers, contract of deeds, application of patent, home studies and all kinds of legal papers. The kind and the number of legalized certificates you need to have will greatly depend on the type of document you have and you need to check how documents works in other countries.