The answer depends on whether only temporary orders have been made (pre-judgment) or whether is a final order (post-judgment). If the matter is the former, service by mail is acceptable. If the matter is post-judgment, personal service is required unless the other parent completes and submits an address verification form that verifies that they mailed the documents to the right address. Under either circumstance, the person serving the paperwork must be someone over the age of 18 other than the party to the action. I strongly discourage the new significant other completing the service of process. Personal service is always acceptable. If you are concerned the other parent may dispose of the paperwork or reject the paperwork, you need not be concerned. The criteria for personal service is that the paperwork is in the other person's general vicinity. If they take the paperwork and throw it back at you or leave it on the ground, service is complete upon placing the paperwork in their general vicinity.