They don't advertise it, but if you start the trial then cancel, it'll downgrade you to the free plan. The features are limited - you have to upload every time and recreate the fields every time, but it works for occasional use.

There was a free trial period that expired, and there was no free option for additional documents that required multiple signers.

I think you just got hit by their marketing page that hides the fact that there's a free plan. I'm on the free plan and I was able to send out a document with three signers. https://rr.judge.sh/Screenshot%202023-07-20%20at%201.03.45%E...