PDF Cross Browser Embed Plugin Wordpress

gistfile1.php

<?php
/*
Plugin Name: PDF Cross Browser Embed
Plugin URI:  http://#
Description: Embeds PDf into a post/page using default media uploader using a cross browser freindly iframe
Version:     1.0 
Author:      Wycks
License:     GPL2


/*  

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License, version 2, as 
    published by the Free Software Foundation.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/

add_filter('media_send_to_editor', 'my_filter_pdf', 20, 3);

function my_filter_pdf($html, $id) {
    $attachment = get_post($id); //fetching attachment by $id passed through

    $mime_type = $attachment->post_mime_type; //getting the mime-type
    if ($mime_type == 'application/pdf') { //checking mime-type
        $src = wp_get_attachment_url( $id );

        $html = '<iframe width="500" height="500" src="'.$src.'"></iframe>';
        return $html; // return new $html    
    }
        return $html;
}
?>

your function closes too early...

    }
    return $html; // return new $html

should read:

    return $html; // return new $html
 }

Thanks, had not noticed.