How do I file a Petition to Modify Child Support? Step 1: Follow the instructions in this packet to fill out the necessary forms.Please note that each court might have their own preferred forms. Edit, sign, and share pima county superior court child support online. No need to install software, just go to DocHub, and sign up instantly and for free. Court Forms and Instructions. Completing the Forms. (2) Petition for Modification of Child Support. (A) Fill in the information requested at top left for the person who is filing this form. Superior Court System - Pima County Superior Court -Quick Court has do-it-yourself forms to file for child support.