[WordPress] Print Friendly Plugin Template Add-On - Add custom classes inside nested iFrames for customization based on Post Type

WP_PF_custom_classes.php

<?php if(is_singular('slug-of-post-type')) :
	global $post;
        $p_type = get_post_type(get_the_ID());
        ?>
        <script type="text/javascript">
            jQuery(document).ready(function() {
                $( ".printfriendly a" ).click(function() {
                    $("#pf-core").load(function() {
                        setTimeout( function () {
                            //console.log( $('#pf-core').contents().find('iframe').contents().find('#pf-print-area') );
                            $('#pf-core').contents().find('iframe').contents().find('#pf-print-area').addClass("pf-<?php echo $p_type; ?>");
                        }, 1000 );
                        // You can lower the milliseconds (1000 by default), if you see a big delay in the way the style is applied, however I dont advise to keep it too low, since the second iFrame will take *a little* time to load anyway... and if the script fires too soon, the style won't be applied at all.
                    });
                });
            });
        </script>
	<?php endif;
	// https://wordpress.org/support/topic/add-body_class-to-iframe-or-dynamically-add-class-references
?>