In order to finalize a divorce, you have to have the other party to a divorce case served with the papers.
The most common way to accomplish this is to hire a private process server or a sheriff to serve the papers on the other party.
However, when you serve the party with these papers, in particular the citation and petition, the petition will say generally what relief you are seeking in your divorce.
If you amend the petition to ask for more relief, then you have to hire a process server to serve the amended petition again.
If you do not do this, you risk having the divorce case reopened for failure to adhere to service of process rules.
You can find a case that somewhat explains this rule for download here.