document generation website - similar to rocket lawyer - english

i run a debt recovery company for small businesses - i would like to create a website that allows my clients to login to a portal, input details (such as their customer contact details) which then creates a document which can be sent out via email, text notification and also a letter, so basically a form builder that leads into a number of different marketing sequences. In total I have around 6 documents (not many) There will need to have a checkout with billing options to signup my client up to also.