If you are offered group life insurance through an employer or organization, you have the right to accept or deny accepting the policy. Unless the life insurance policy is designed to protect the interests of the company, the employer does not have any insurable interest which might give them an incentive to require purchasing the coverage. Signing the form which states you understand and choose to refuse coverage should be all that is required.
If you look at the question from a legal standpoint, you are the one being solicited for coverage, and whether or not you choose to pay insurance premiums is a free choice. You cannot be required to take an extra step to prove you are turning down the coverage because you are not the one who initiated the contact, so to speak. If notary services are needed, the insurance representative who meets with you is most likely bonded and authorized to handle the task as a matter of course.
Life insurance is a necessary commodity, but we are all free to choose where, when and how much coverage to buy. If you do not already have life insurance, it might be a good idea to give the group life insurance policy some consideration. If you are under 30, your rates will be very affordable, and buying a life insurance policy while you're relatively young is the best way to avoid future denials due to medical conditions which develop over time. Do not blindly buy into a policy you are not comfortable with, but take the time to make sure that your loved ones and obligations are taken care of if something terrible should happen.
Legally, your signature is your contractual mark. For example, you do not need to notarize your signature when you get a driver's license or apply for a credit card. Your unique mark is enough, and notarized signatures are reserved for circumstances where verifying the signature may be difficult to do at a later time. For example, selling your car would require notarizing the title so that the buyer would not have to have you physically present when they went to get the vehicle registered.