Problems with PDF file

Question

I am showing a PDF file directly in the browser. In Google Chrome, it works perfectly, but if you use Firefox, the PDF is as shown below.

Did you have to put some extra config for Firefox? The PDF file is ok, open directly in the folder.

Controller Code

public ActionResult Boleto(string id)
{
    var arquivoPDF = Path.Combine(MegaBoleto.PastaPDF(), String.Format("{0}.{1}", id, "pdf"));
    if (System.IO.File.Exists(arquivoPDF))
    {
        return File(arquivoPDF, "application/pdf");
    }
    return View();
}