How to print two documents on button click?

if (Page.IsValid)
            {
                TextBoxUser_ID.Text = Session["user_id"].ToString();
                ClientScript.RegisterStartupScript(this.GetType(), "onclick", "<script language=javascript>window.open('ReportFormFTE.aspx','PrintMe','height=650px,width=950px,scrollbars=1');</script>");
                ClientScript.RegisterStartupScript(this.GetType(), "onclick", "<script language=javascript>window.open('ReportFormGrad.aspx','PrintMe','height=650px,width=950px,scrollbars=1');</script>");
                ScriptManager.RegisterStartupScript(this, typeof(Page), "myscript", "alert('You have successfully submitted the electronic portion of the General and Enrollment Profile.  Please send your signed Profile along with any required attachments to SACSCOC, Attn: Profiles, 1866 Southern Lane, Decatur, Ga 30033.');location.href='WelcomeMenu.aspx';", true);
            }
        }