In OpenSolar, you can configure your settings to automatically send the customer a PDF copy of the proposal and/or contract when they sign & accept. You can send them the PDF and contract combined, or each document separately.
To set this up, navigate to control > purchase experience > checkout experience.
Here, toggle on "Email proposal and contract PDF to customer on proposal acceptance"
You can decide whether you want to share the combined proposal and contract, proposal only, or contract only.
You can set the email subject and an email message that will send to your customer upon acceptance. The documents will be attached to this email that gets sent to them.
Now, when your customers accepts and signs your proposal, they will get the files sent to them automatically with the email subject and message that you set. For example: