I'm going to take a minute here and we're going to cover how to properly do an all-purpose acknowledgement for the state of California. An acknowledgment is one of the most common types of notarial acts, but it often confuses Notaries.Here are 5 steps to performing an acknowledgment. An Acknowledgment of Paternity (AOP) is a legal document that allows parents who aren't married to establish legal paternity. An acknowledgment copy will be returned to the filer, along with an acknowledgment letter, detailing what was indexed into the Filing Officer's indexing system. You must use the filing application to generate the form and print it from there.