You can get fillable forms online, except for the Summons. You must get the Summons form from the Court Clerk. The Court charges $5.00 for a signed Summons form.
Get the other forms you need (including instructions) here: Maine Divorce without Children Forms (fillable .pdf's and "interview-and-answer" automated forms ).
Or you can go to your local District Court and ask the clerk for a forms packet. Tell the clerk that you are married and whether you own property (a house or land). The clerk will give you the right set of court forms. The packet also has a page of instructions telling you what to do with the forms and how to "serve" your spouse with the forms.
Again, here are the typical costs of getting a divorce:
If you have a very low income and cannot pay these costs, you can ask the court to pay them for you. Go here to get the forms online. Or ask the clerk for the forms: an Application to Proceed Without Payment of Fees (fee waiver form) and an Indigency Affidavit. Check all of the boxes near the top of the fee waiver form to show that you need all costs waived. On the affidavit form, list all of your income and expenses. If you get TANF, SSI, or general assistance, the court should waive the fees. (Contact Pine Tree Legal Assistance if you are denied). If your income is higher, the court will look at your income and expenses and decide whether you qualify for the waiver.