A Notary Public is required to authenticate (certify) your document(s) if they are being sent outside England and Wales (This includes Scotland and Northern Ireland as well as every other country in the world). The Notary Public will have to sign and place their seal on the document that can then be sent to the receiving country.
Please note that all documents going abroad will be valid only if Notarised by a Notary Public. If they are not Notarised by a Notary Public, they will be rejected by the receiving country. Solicitors can often claim that they can certify such documents, however unless they are a Notary Public, their certification will be invalid and will often not be accepted.