Quotes and Invoices are only applicable to our Business and Enterprise plans: https://www.postman.com/pricing/
New customers can send an email to firstname.lastname@example.org to get started.
For existing customers, pending payments are listed at https://app.getpostman.com/pay/billing. These can be paid online, or via check/wire-transfer. Offline payment instructions are on the invoice that's sent to the registered billing email address as a PDF file.