This plugin lets you display a custom signature at the bottom of your posts. Simply type the text you want in the options page and configure it to display on every post, or manually display it by adding the trigger text wherever you like. You can also add in author information using the included variables - login name, first name, last name, nickname, email address, website, and description/bio. It get this information from the author’s account settings.
Add Signature Plugin, WordPress, Plugins, WordPress Plugin