True.
A notary public should not notarize a document if they have a pecuniary (financial) interest in the transaction. This is because it would create a conflict of interest and potentially compromise the impartiality and integrity of the notarization process. Notaries are expected to act as impartial witnesses to the signing of documents to prevent fraud and ensure the authenticity of signatures. Having a financial interest in the transaction could undermine this impartiality and is generally considered unethical and, in some jurisdictions, illegal.