Owners and admins of the account have access to the Billing Contact page in the portal.
First, click Account Details, then click Billing:
Next, click the Billing Contact tab, fill out the form and click Submit. This will update the billing information that is on file for the account. The email address provided on the form is the email that will receive billing invoices.
Please contact support@documo.com or billing@documo.com to add additional email addresses for receiving invoices.