I gather this document is authenticated by a Notary Public, hence my reasoning for translating "notas" as a notorial act/instrument/writing. Mário's suggestion is also a good way of putting it, although a bit generic. So, I'm just giving you another option to consider.

http://en.wikipedia.org/wiki/Act_(document)

Notarial Acts

A notarial act (or notarial instrument or notarial writing) is any written narration of facts (recitals) drawn up by a notary public or civil-law notary authenticated by his signature and official seal and detailing a procedure which has been transacted by or before him in his official capacity. A notarial act is the only lawful means of proving those facts of which it is the recognized record, whereas on other matters it is usually inadmissible, because, being beyond the powers entrusted to the notary by law, it is non-official. In most common-law countries, multiple-page acts are bound together using a sewn or knotted ribbon (referred to as silk), the ends of which are secured by a wafer impressed with the notary's seal. This is called annexing or annexure.

http://www.asnnotary.org/?form=termsanddefinitions