Add a separate recipient field for each recipient by clicking the "Add Recipient" button.

In the first recipient field, put in the name of one recipient and enter the email address. In the second recipient field, put in the name of the second recipient and enter the email address.

On the document itself, you will be able to drag a signature icon and an initial icon to the appropriate area. As you have two recipients, each icon will be a different color so you can keep straight which is which.

You didn't say if you're sending this one document to the same email address or not, but this process will still work. That particular email address will just receive two separate emails - one email will refer to recipient #1's name and the other email will refer to recipient #2's name.