Using a notary for important documents is crucial because it provides an additional layer of authentication and security, ensuring the document's legitimacy and preventing fraud. A notary verifies the identities of the signing parties, confirms their willingness to sign without coercion, and adds an official seal, which makes the document legally recognized and harder to dispute in court. Notarized documents are often required for significant transactions and legal matters, like property sales, wills, and business contracts, as they add credibility and protect all parties involved by creating a trusted record.