Merge Two or More Crystal Report in PDF

using (var reportDocument = new ReportDocument())
{
    var datasource = new Datasource { EnforceConstraints = false };

    var adapter = new adoTableAdapter { Connection = ConfigurationManager.ConnectionStrings["ConnectionString"]) };
    adapter.Fill(datasource.ado);

    reportDocument.Load(RptPath);
    reportDocument.SetDataSource(datasource);

    PageMargins myMargins = reportDocument.PrintOptions.PageMargins;
    myMargins.topMargin = Settings.Default.DefaultTopMargin;
    myMargins.leftMargin = Settings.Default.DefaultLeftMargin;
    reportDocument.PrintOptions.ApplyPageMargins(myMargins);
    reportDocument.PrintOptions.PaperSize = PaperSize.PaperA5;
    reportDocument.PrintOptions.PaperOrientation = PaperOrientation.Landscape;

    reportDocument.ExportOptions.ExportDestinationType = ExportDestinationType.DiskFile;
    reportDocument.ExportOptions.ExportFormatType = ExportFormatType.PortableDocFormat;
    reportDocument.ExportOptions.DestinationOptions = new DiskFileDestinationOptions { DiskFileName = PdfFilename };
    reportDocument.ExportOptions.FormatOptions = new PdfRtfWordFormatOptions();

    reportDocument.Export();
}