Convert Hardcopy sales forms to soft copy forms

I have 4 sales quotation forms to convert an online version. There are some requirements: - I will be using this on tablet or smartphone. So it has to be mobile responsive - Client needs to sign. So i need to capture signature - After signing, it has to generate a PDF version of the signed form. - Fields can be exported out to a database. Preferably via Zapier - PDF version of sign form can be customized to look like a traditional sales order form - along with static content (terms and conditions, etc) - Sales Order Form needs to have pricing selection. I.e. customer selects the items he wants, and the pricing is automatically calculated. - The form must be able to be edited easily (without having me to program) - The form should be able to work without internet( preferably) - The form should have a save function.. So if the customer fills up halfway, they can return again to continue filling up. - I should be able to create new forms on my own I have already evaluated several software. Prefer it to be Saas solution. But so far the solution that can meet my needs is Gravity Forms. The problem with Gravity forms is that it requires a developer to customize the codes. 1) Let me know your solution - it can even be a simple sass solution. 2) We can still stay with Gravity forms if it's the only way