public static bool MergePDFs(List <string> files)
        {
            string intrayPath    = SimpleServerExtensionMethods.GetIntrayPath("DMSArchiv");
            string firstFileName = Path.GetFileName(files.First());
            string targetPath    = Path.Combine(intrayPath, firstFileName);

            try
            {
                using (PdfDocument targetDoc = new PdfDocument())
                {
                    foreach (string fileName in files)
                    {
                        using (PdfDocument pdfDoc = PdfReader.Open(fileName, PdfDocumentOpenMode.Import))
                            for (int i = 0; i < pdfDoc.PageCount; i++)
                            {
                                targetDoc.AddPage(pdfDoc.Pages[i]);
                            }

                        File.Delete(fileName);
                    }
                    targetDoc.Save(targetPath);
                }
                return(true);
            }
            catch (Exception ex)
            {
                logger.Error(ex.Message);
                logger.Error(ex.StackTrace);
                return(false);
            }
        }
        public static bool SplitPDFs(List <string> files)
        {
            string intrayPath    = SimpleServerExtensionMethods.GetIntrayPath("DMSArchiv");
            string firstFileName = Path.GetFileName(files.First());

            int pageNumber;

            try
            {
                foreach (string fileName in files)
                {
                    pageNumber = 1;
                    string pathName     = Path.GetDirectoryName(fileName);
                    string fileNameOnly = Path.Combine(pathName, Path.GetFileNameWithoutExtension(fileName));

                    using (PdfDocument pdfDoc = PdfReader.Open(fileName, PdfDocumentOpenMode.Import))
                        for (int i = 0; i < pdfDoc.PageCount; i++)
                        {
                            using (PdfDocument targetDoc = new PdfDocument())
                            {
                                targetDoc.AddPage(pdfDoc.Pages[i]);
                                string targetPath = fileName.Replace(fileNameOnly, fileNameOnly + "_" + pageNumber.ToString().PadLeft(4, '0'));
                                targetDoc.Save(targetPath);
                                pageNumber++;
                            }
                        }
                }


                foreach (string pdf in files)
                {
                    File.Delete(pdf);
                }

                return(true);
            }
            catch (Exception ex)
            {
                logger.Error(ex.Message);
                logger.Error(ex.StackTrace);
                return(false);
            }
        }