public void createPdfButton_Click(object sender, EventArgs e)
    {      
                    string brandId = pdfBrandDropDownList.SelectedValue;
                    string catId = pdfCategoryDropDownList.SelectedValue;                  

                    Response.Redirect("stampapdf.aspx?braId=" + brandId + "&catId=" + catId +"&pag=catalogo");               
     
    }