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();  
}