Yes, it is $125.87 USD per year for the sign plan only.
There are no other pre-requisities for the Adobe Sign app. I log in through my web browser. Clients can also use the app on their phone. I make sure to have it as actual signatures only. They can take a picture of their signature or draw their signature. I use it for other accounting forms I get signed as I have clients far away from me.
I am currently testing out Signnow. For a part time proprietor like myself price is reasonable at $96 USD per year for a single user. With unlimited signing.
Docusign is pricier at $396 CAN per year, but will be integrated with taxcycle, so that counts for something. If they offered $99 off to taxcycle users I would go for it.
Otherwise my other option is to pay for the months that I need it (Mar and Apr) at $50/mth and not worry about rest of year.