How to Force Download mpdf Files Using Ajax

Question

I am trying to download pdf files using the library mpdf.

Calling the php page in the browser it works normally.

Example:

require_once 'mpdf/mpdf.php';

$mpdf = new mPDF();

$boleto = '<h3>Boleto</h3>';

$mpdf->WriteHTML($boleto);

$mpdf->Output('teste.pdf',"D");

Now if I try to call it an html page using ajax its return looks like this:

As I call Ajax:

var salvarBoleto = function(parcelas) {
  $.ajax({
    url: boletoUrl,
    data: {
      "acao": "salvarBoleto",
      "parcelas": parcelas
    },
    dataType: 'json',
    type: 'POST',
    success: function(data) {

    },
    error: function(data) {
      console.warn("mostrar msg de erro");
    }
  });
};

Normally I call a new tab to issue the pdf, but in this case I would like to do it on the ajax page.