index.aspx.cs

protected void Page_Load(object sender, EventArgs e)
{
    // execute only when loaded from IFRAME
    if (Request.QueryString["download"] == "1")
    {
        if (Session["document"] == null)
            return;

        // return the stored document
        Response.Clear();
        Response.ContentType = "application/pdf";
        Response.AddHeader("Content-Disposition",
            "attachment; filename=results.pdf");
        Response.BinaryWrite((byte[])Session["document"]);
    }
}