@Mr B is me Within the standard user interface of Acrobat Sign, there is no direct "Set as Default" button to permanently select Acrobat Sign. You could as a work-around is work with a custom template, a way to avoid repeating steps—especially for setting Acrobat Sign as the authentication method?!
Start a new send and set everything the way you want: upload the document, adjust agreement settings, and add a placeholder recipient. Set authentication for the placeholder to Acrobat Sign in the recipient settings. Save as a template instead of sending. Give it a clear name like “Standard Signature - Acrobat Sign Authentication” . Use the template next time you send. Just update the placeholder’s name and email—the authentication method will already be set. This way, you only configure it once, and reuse it every time—saving clicks and effort.