I would like to confirm that "IntuitKaiXiang" is correct - the way to change the footer of the customer statement is by changing the invoice template. There is no place to edit a template specifically for the customer statement, rather the customer statement will use the same template as your invoices. I have multiple invoice template styles, but it appears that my customer statement was using whichever template is designated as the "Master" form type. This is shown on the custom form styles page (Gear Icon -> Custom Form Styles). By editing the Master template you can update the information shown on your customer statements.