To get a document notarized, the notary MUST witness the document being signed. That's what notarizing means, that the notary has seen the document signed, and has examined the ID of the person who signs it.
Notarizing a document does NOT make a document "legal", it only means that someone showed up with a document, signed it in the presence of a notary, and presented proper ID. Notary publics generally don't even read the documents that they notarize, and they won't give a legal opinion about the document unless they also happen to be a legal professional and you pay them for their opinion, as well as notarizing the document. If the document is illegal, for instance it's a contract to perform criminal acts, notarizing the document won't make it valid.
Let a lawyer look at the document first, to make sure it's legal, if this is important to you.