When you sign a document using your Notes client, a unique portion of your user ID is attached to the signed note to identify you as author. Only new documents can be signed and the signature cannot be removed once the note is stored. Signing is especially valuable with documents to be mailed.

To sign an AbtLnNote, use the sign method. The signature will be included, but the document is not actually signed until it is stored. A document which receives the sign message can be unsigned with the unsign method so long as it was not stored.