Someone abroad tells you to send a “certified copy,” or a “notarized copy,” or an “apostilled document.” These are not synonyms, and the wrong one is rejected.
Certified copy
A copy issued by the office that holds the original record: a county recorder, a vital records office, a court clerk. It carries that office’s seal. This is what you need before an apostille on a government record, not instead of one.
Notarized copy
A notary attests that a copy matches an original they were shown, or witnesses a signature. This applies to private documents, and to some academic records. A notarized copy of a birth certificate is generally not accepted by states in place of a certified copy, because the state wants its own record, not a notary’s opinion of it.
Apostille
A certificate confirming that the seal or signature on a document is genuine, so a foreign government will accept it. It sits on top of one of the above, and does not replace either.
Working out what you were asked for
The reliable signal is the destination country, not the wording. If the document is going abroad, an apostille or legalization is almost certainly involved, and the question is only what has to happen first.
If the request you were given is ambiguous, send us the exact wording. Interpreting what a foreign authority actually wants is a large part of what we do, and it is free to ask.