Requiring all people in an organisation to login before signing documents

I work in an organisation that has a number of Adobe DC users and are currently setup for Federated ID.

For a couple of reasons we want everyone in the organisation to login before they are able to sign a document that was sent to them, however most people in the organisation dont currently have Adobe ID accounts.

What's the best way to achieve this? 

* Does every user need an Adobe DC license? 

* Do we need to pre-create Adobe ID accounts for everyone who may need to sign?