To create a reusable form that you can have any participant sign on your site or by emailing the URL, start by uploading a document as normal (please see the Sending Documents for e-Signature articles).
When you get to the Add Participants screen, click the +Advanced link at the bottom right.
This will open the Advanced sidebar.
Click the Make this a Form button.
Confirm to making the document as a reusable form.
Only one outside participant can be on a reusable form. (The sender can be added as a participant also using the I need to sign button.) You will see the participant change to Form Participant.
Continue to place fields on the document as normal.
Enter the Document Name and press the Save As Form button.
You will get a URL that you can save and use as many times as you like for anyone to sign.
You can also get this URL on the Documents screen for a Reusable Form.