Open pdf from a link (colissimo)

Question

I want to open a pdf on the same page when I click on a link generated by colissimo. (https://ws.colissimo.fr/) I want to open it on the active tab, no dialog should open. I want to do this in jquery, I tried a lot of solutions like "window.location.open" or "window.location.replace" but nothing works.

I have a link who call my function on click :

<p id="btnPrintPdf">
  <a href="javascript:void(0)" onclick="showPdfEtiquetteRetour(<?php echo $order->commande_id; ?>, <?php echo $multi_transp; ?>, '<?php echo $bon_retour_numero; ?>', true)"></a>
</p>

and this is a part of my jquery function :

$.ajax({
        url : path_relative_root + 'ajax_create_etiquette.php',
        type : 'post',
        data : data,
        success : function (res) {
            if ( res.substr(0,5) == 'false' ) {
                alert('js_error_return_label');
            } else {
                if (show_pdf) {
                    window.open(res);
                } else {
                    location.reload();
                }
            }
        }
    });

res is a link to the pdf