Merge rdlc's rendered as pdf in ActionResult

[AllowAgencyUser]
        public ActionResult TrainingHours(int id)
        {
            EmployeeModel model = new EmployeeModel(id);
            if (!model.CheckEmployeeAccess())
                throw new HttpException(403, "Access Denied");
 
            byte[] report = model.GetTrainingHoursReport(id);
            return File(report, Constants.PdfMimeType, model.EmployeeHoursReportFileName);
        }

[AllowAgencyUser]
        public ActionResult MassTrainingHours(int[] employeeIds)
        {
            if (employeeIds == null)
                return new EmptyResult();
 
            List<byte[]> reportsList = new List<byte[]>();
            foreach (int employeeId in employeeIds)
            {
                EmployeeModel model = new EmployeeModel(employeeId);
                byte[] fileBytes = model.GetTrainingHoursReport(employeeId);
                reportsList.Add(model.GetTrainingHoursReport(employeeId));
            }
            PdfMerger merger = new PdfMerger();
            byte[] report = merger.MergeFiles(reportsList);
            return File(report, Constants.PdfMimeType, "training_hours.pdf");
        }

public byte[] MergeFiles(List<byte[]> inputFiles)
        {
            MemoryStream outputMS = new MemoryStream();
            Document document = new Document();
            PdfCopy writer = new PdfCopy(document, outputMS);
            PdfImportedPage page = null;
 
            document.Open();
 
            foreach (byte[] fileData in inputFiles)
            {
                PdfReader reader = new PdfReader(fileData);
                int n = reader.NumberOfPages;
 
                for (int i = 1; i <= n; i++)
                {
                    page = writer.GetImportedPage(reader, i);
                    writer.AddPage(page);
                }
 
                PRAcroForm form = reader.AcroForm;
                if (form != null)
                    writer.CopyAcroForm(reader);
            }
 
            document.Close();
 
            return outputMS.ToArray();
        }