Collect payments and fees applied

Hello,

I'm going to use adobe sign to get my customers to sign the quotes I send them.

Now I also need them to pay a percent of the quote.

I saw that I need a braintree account to do so : is it mandatory ?

Also I was wondering how much it cost : I guess I'll have to pay a fee on each transaction ?

Could you please tell me a little but more ?

Thanks

Regards