I had an enquiry for a document that needed to have one signature in Melbourne and one signature in Perth. Both signatures needed to be witnessed by a Public Notary. DFAT will only issue an authentication or apostille for one notary. There are two options to move forward:
1. Have two documents which are ‘Counterpart’ documents, or
2. One document but have only one Public Notary’s work verified
If I put myself in the receivers shoes I would want to know that both Public Notaries were recognised and therefore I could rely on the signature being correct and verified. The Counterpart documents should reference each other. If you have two documents then each would need an apostille/authentication.

Ultimately whoever is accepting the final authenticated document can state their preference whether they are happy with option 1 or 2.