signing adobe fillable forms

I'm sure there's a simple answer to this!

I'm in charge of an event that requires submission of fillable registration forms. I know how to distribute and collect those and have been doing that for years. But this year - for the first time - each registration form requires two digital signatures. I can't ask the applicants to download an app or log into an unknown (to them) third-party website in order to do that. Surely, there's a simple way to accomplish this via some form of Acrobat. I've had Creative Cloud for years and would even be open to buying something additional - if I have to. But I can NOT ask my applicants to spend money in order to be able to sign my forms. Could someone please help??? I will be so very grateful!!!