Upload PDF

  FileUpload fl1 = (FileUpload)pnl2.FindControl("FileUpload2");
                UploadImage(fl1);
                sPath1 = UploadImage(fl1);
                if (sPath1 == "File size cannot be larger than 2 MB")
                {
                    lblSuccess.Text = sPath1;
                    return;
                }

 private string UploadImage(FileUpload fl)
    {
        string sSavePath = string.Empty;
        string sSavePath1 = string.Empty;
        string sFilename = string.Empty;
        string msg = string.Empty;
        Random RandomClass = new Random();
        int RandomNumber1 = RandomClass.Next(1000, 9000);

        // Set constant values
        string type = fl.PostedFile.ContentType;

        //code for jpg file
        if (fl.HasFile && checkImageContentType(fl.PostedFile.ContentType))
        {
            // HttpPostedFile fl = fl.PostedFile;
            if (fl.PostedFile.ContentType != "application/pdf")
            {
                System.Drawing.Image oImage = System.Drawing.Image.FromStream(fl.PostedFile.InputStream);
                if (oImage.Width > 150 || oImage.Height > 150)
                {
                    lblSuccess.Text = "Image is greater than 150 * 150";
                    completepath = lblSuccess.Text.ToString();
                    return completepath;
                }
                else
                {
                    sSavePath = "Brochure/";
                    sFilename = fl.FileName;
                    sFilename = "Press" + Convert.ToString(Session["exid"]) + RandomNumber1 + "_" + fl.FileName;
                    fl.SaveAs(Server.MapPath(sSavePath + sFilename));
                    completepath = sSavePath + sFilename;
                    return completepath;
                }
            }
            else
            {
                if (((Convert.ToDecimal(fl.PostedFile.ContentLength) / 1024) / 1024) > 2)
                {

                    lblSuccess.Text = "File size cannot be larger than 2 MB";
                    return lblSuccess.Text;
                }
                else
                {
                    sSavePath = "PDF/";
                    sFilename = "Press_" + Convert.ToString(Session["exid"]) + RandomNumber1 + "_" + fl.FileName;
                    fl.SaveAs(Server.MapPath(sSavePath + sFilename));
                    completepath = sSavePath + sFilename;
                    return completepath;
                }
            }
        }
        else
        {
            return msg;
        }
    }
    public static bool checkImageContentType(string contentType)
    {
        //check whether the uploaded file is an image or not
        if (contentType == "image/gif" || contentType == "image/jpeg" || contentType == "image/pjpeg" || contentType == "application/pdf")
            return true;
        else
            return false;
    }

 <asp:FileUpload ID="FileUpload2" runat="server" />
                                        <asp:RequiredFieldValidator ID="RequiredFieldValidator2" runat="server" ControlToValidate="FileUpload2"
                                            ErrorMessage="Required" Display="Dynamic">Required</asp:RequiredFieldValidator><br />
                                        <asp:RegularExpressionValidator ID="RevDoc" runat="server" ControlToValidate="FileUpload2"
                                            ErrorMessage="select only PDF file." ValidationExpression="^.+(.pdf)$" Display="Dynamic"><span style="color: Red">select only PDF file</span> </asp:RegularExpressionValidator>
                                        <a id="Pdf" target="_blank" runat="server"></a><span id="err2" style="color: Red">