I'd like the customer to be able to e-sign the proposal I send them and pay at the same time to make sales process seamless.

I'd like the customer to be able to e-sign the proposal I send them and pay at the same time to make sales process seamless. Currently, I am having to print proposal for customer to sign manually and have customer go in to customer portal to put in credit card info before paying for initial invoice. I am aware about the "Buy Now" option I can put on my site but at this time, I do not plan on adding it due to the various package options we offer.