C#调用系统注册程序打开pdf文件

private void btn_帮助文档_ItemClick(object sender, ItemClickEventArgs e)
{
    try
    {
        System.Diagnostics.Process.Start(@"..help软件系统帮助文档.pdf"); 
    }
    catch(Exception ex)
    {
        MessageBox.Show(ex.Message);
    }
}