How Can I Solve This Error "File Does Not Begin With %Pdf- C:\Users\Tom\Local\Temp\Pdf6496.Tmp" Which Always Occurrs Whenever I Try To Run My Code For Printing.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using CrystalDecisions.CrystalReports.Engine;
using CrystalDecisions.Shared;

public partial class Compassion_forms_Parternship_Committee : System.Web.UI.Page
{
    ReportDocument children = new ReportDocument();
    protected void Page_Load(object sender, EventArgs e)
    {

    }
  protected void btnPrintRegisteredChild_Click(object sender, EventArgs e)
    {
        //Code For Printing Out The Registered Children
        try
        {
            using (DataSetCompassion childrenlist = new DataSetCompassion())
            {
                using (DataSetCompassionTableAdapters.childrenTableAdapter childrens = new DataSetCompassionTableAdapters.childrenTableAdapter())
                {
                    childrens.FillByChildren(childrenlist.children, txtChildApproval.Text);

                }

                crChildrenViewer.Visible = true;
                children.Load(Server.MapPath("~/CrystalReportChildren.rpt"));
                children.SetDataSource(childrenlist);
                crChildrenViewer.ReportSource = children;
                children.ExportToHttpResponse(ExportFormatType.PortableDocFormat, Response, false, "receipt");
                children.Dispose();


            }
        }
        catch (Exception ex)
        {

            lblPrintChildError.Text = ex.Message.ToString();
        }
    }