How can I change pending submissions

Are you referring to changing/editing Incomplete Payment submissions?

https://www.jotform.com/help/564-how-to-view-incomplete-payments-of-your-payment-forms/

I'm afraid that you cannot edit incomplete / pending submissions - only completed submissions can be edited. So in case you want to edit an incomplete submission, you will have to complete it first, in one of the ways described in the following guide:

https://www.jotform.com/help/272-Paypal-Incomplete-Payments-FAQ

If you needed assistance with something else instead, please let us know in a little more detail what you were referring to by changing pending submissions, and we will be happy to help. Thank you.