Portugal - diplomas, references, recommendation or proof of good conduct

Do I need to send diplomas with my application?

Not unless it is mentioned in the advertisement. Take a copy to the interview, however. If your application is successful, documents may be requested when formalising the contract.

When taking copies of diplomas or qualifi­cations to the interview, be selective, and be aware that Portuguese employers may be unfamiliar with your country of origin's edu­cation and training system and the relevant knowledge and skills content. Documents such as the Europass diploma supplement or certifi­cate supplement may be more useful.

Should I supply references, letters of recommendation or proof of good conduct?

It is not common practice in Portugal to ask for references or to go through letters of recommendation, although some employers might see these as a plus.