When documents need to be proper acknowledgment, they need to be taken to a public notary. This person will sign and stamp the document with a legal seal to officially notarize the paper. Each notary's seal is different, like a legal fingerprint. Often, this person will witness you signing a jurat (an oath at the foot of an affidavit that states where, when, and before whom the document was signed) claiming the paper to be an original or a certified copy of the original before singing it themselves.
Notary agents have been around since ancient Rome, where the slave Tiro developed the shorthand system "notae" for taking down the speeches of Cicero. Six hundred years later, the law school of Bologna used Tiro's methods to create the first real notaries. These folks prepared financial papers, wills, and other contracts for a fee. Soon the need for notaries spread all over Europe and migrated with the colonists to America in the 1600s. Only the most upstanding citizens were appointed as public notaries in the colonies since it was their job to certify and keep papers safe. Since then, the biggest responsibility of the notary has become to make sure papers like property deeds, power of attorney, mobile vehicle titles, and financial loans are true copies and not forgeries.
These officials are appointed by the state. They cover personal and business certificates for things like mobile travel and loans while maintaining a sense of impartiality. A notary is tested often to make sure they never turn away service because of a person's race, gender, religious affiliation, sexual orientation, nationality, or political ties.