Giving Estimate to client's - they can read and sign?

We need to give different Bride's an Estimate that they can sign off on and then we would send them a contract with a down payment to finalize and hold their dates.

How do we do this with out our url changing with every bride? 

As I can understand, you need to receive submissions, review them and send them back a file so your users can review it as well and send it back to you. Please let me  know if I did not understand correctly. 

If I'm correct on my understanding, I think you could simply ask your users to submit the form, then you review it and fill out the needed fields or attach the needed files, then send the form to them again using an email auto-responder. 

Once they get the email with the required information, they may sign or attach any additional file and send it back to you.

This guide will help you adding an email auto-responder to your form: https://www.jotform.com/help/26-Setting-Up-an-Autoresponder-Email 

You would also need to set the auto-responder to be sent only when editing the submission, this option can be found under the advanced tab:

This guide will help you to allow file uploads on your form: https://www.jotform.com/help/332-How-to-Create-File-Upload-Forms 

Now, regarding the payments, it's not possible to send payments once the form has been submitted once (or when editing a submission), the payment will need to be done when the first submission is sent. 

If you would like to receive payments, you would need to create a separated form for that and that may be the final step; however, you would still be able to calculate the payment amount on your initial form and then pass it to the payment one. 

Please let us know if you would like to apply this workflow for your payments so we can further help you.