You can definitely submit an offer without a buyer's agent (we just did this successfully with no issues) - the listing agent should have you sign paperwork that they are not representing you, but they are just facilitating the transaction.
Not every document that needs to be signed needs to be notarized — only certain types of paperwork require a notary's seal. While laws vary from state to state, they typically include real estate transactions, certain legal documents, many financial documents, and some forms related to healthcare.
In most cases, a contract does not have to be notarized since the signed contract itself is enforceable and legally binding in state or federal courts. Many types of written contracts don't require a notary public to be valid.
REALTORS® are negotiation experts. If you buy a home without an agent, you'll have to negotiate and decide how much to offer on your own. This may cause you to unknowingly overpay for your home – or lose out on one you want.