What is correct about digital signatures?

When a document is signed, the signer's private key encrypts a hash derived from that document's exact content, producing a signature that is mathematically unique to that document. Copying the signature to a different document would cause verification to fail because the recipient's computed hash of the new document would not match the decrypted hash embedded in the signature. This property, called non-transferability, is a fundamental guarantee of digital signature schemes.

Digital signatures are not reusable across documents of the same type because each signature is computed from the unique hash of one specific document's content.

A digital signature is an encrypted hash value, not plain text; attaching a plain-text string to a document provides no cryptographic integrity guarantee.

Digital signatures are not issued as long-lived reusable tokens; each signing operation produces a unique output tied to the exact content being signed at that moment.