// Pull PDF links from posts for category pages
function pdf_links() {
    global $wpdb;
    $attachment_id = $wpdb->get_var("SELECT ID FROM $wpdb->posts WHERE post_parent = '$post->ID' AND post_status = 'inherit' AND post_type='attachment' ORDER BY post_date DESC LIMIT 1");
    $attachment_url = wp_get_attachment_link($attachment_id);
    if($attachment_id == NULL){
        echo '';
    } else {
        echo wp_get_attachment_link($attachment_id, '' , false, false, 'Download PDF');
        echo $attachment_url;
    }
}