Thanks to a post on wpmu.org I found how to add a signature to a WordPress post by adding script in the functions.php file.
add_filter('the_content','add_signature');
function add_signature($text) {
global $post;
if($post->post_type == 'post') $text .= '<div class="signature">
<img src="http:/yoursite.com/wp-content/themes/yourtheme/images/signature.png" alt="signature" />
</div>';
return $text;
}
They also suggested the following if you need to tweak the placement of the signature.
div.signature img {
padding: 5px;
}
