So what you really want is for your signature's appearance to contain user's ID and signing time. To do that you sign PDF with a regular digital signature and apply custom appearance to it. The "Sign" dialog contains "Appearance" field that has a drop-down list on the right which lists all available appearances and a "Create New Appearance" button. The standard/default signature appearance already contains signing time. You can create a custom appearance that includes additional information that you want to appear there. If you want your username to appear in the signature appearance you create an image file that contains your username and add this image to your custom appearance.
Multiple users can definitely sign the same PDF. Usually the signing certificate owner's name appears in the certificate itself and is included in the standard/default signature appearance. This is not Windows username but still identifies the signer, IMO better than Windows username. I do not think you want to disclose your password by placing it in the signature appearance.
You keep mixing two completely different and unrelated concepts: authentication and signing. I still do not understand what exactly you mean by "authentication". It has nothing to do with signature.