WHy offer a 7 day free trial if it doesn't work???

You are just trying to use Send for Signing? That's a separate service, not part of Acrobat. And it's available also with the free Reader.

Sounds as if you are confusing two products: Acrobat Pro and Acrobat Reader. At least, most people do. They are different apps, and you need to check which one you are using. Acrobat Reader does not change.

Be sure to cancel if you don't want to start paying.