How do you add signatures for two people on one document, WITHOUT sending to two participants?

Hi there! I am a marriage celebrant, and I usually only have one of the party's email addresses to send my contract to, however, the contract has to be signed by both parties.

I'm struggling to work out how to add two signature fields without having to send to two separate participants. I want to be able to send the contract once, to one email address, but have the couple sign individually.

Cheers,

Sam