Preventing download Option from pdf file using iframe

<asp:Panel ID="pnlDisplay" runat="server" Visible="true" Width="100%">
   <iframe width="700px" runat="server" height="800px" id="myPDF"></iframe>
</asp:Panel>

protected void grdArticles_RowCommand(object sender, GridViewCommandEventArgs e)
{
   if (e.CommandName == "View")
   {
      DataSet ds = obj.getArticlebyId(Convert.ToInt32(e.CommandArgument));
      if (ds.Tables[0].Rows.Count > 0)
      {
         lblTitle.Text = ds.Tables[0].Rows[0]["ArticleTitle"].ToString();
         lblAritcalContent.Text = ds.Tables[0].Rows[0]["ArticleContent"].ToString();
         string pdffile = ds.Tables[0].Rows[0]["PdfPath"].ToString();
         //string pdf1 = "PdfArtical/" + "Test.pdf" + "#toolbar=0&navpanes=0";
         string pdf1 = pdffile;
         myPDF.Attributes.Add("src", pdf1.ToString());
         //myPDF.Style.Add("display", "none");
      }
      else
      {
      }
   }
}