使用ItextSharop合并pdf文件，体积变大的解决

通用的合并方式导致输出的pdf 文件中嵌入了大量的重复字体。导致文件体积膨胀。

使用基于内存流的方式，读取文件字节，可以解决重复字体的嵌入问题；

   public static string MergeFiles(string targetPdfFilesDir)
        {
            string outPath = string.Empty;
            //验证文件是否存在
            if (!Directory.Exists(targetPdfFilesDir))
            {
                throw new FileNotFoundException("指定的目录不存在：" + targetPdfFilesDir);
            }

            var filePathList = Directory.EnumerateFiles(targetPdfFilesDir, "*.pdf");
            if (filePathList.IsEmpty())
            {
                return outPath;
            }

            //合并pdf文件

            string runningDir = AppDomainTypeFinder.Instance.GetBinDirectory();

            outPath = Path.Combine(runningDir, "temp", Guid.NewGuid().ToString() + ".pdf");

            MergeFiles(outPath, filePathList.ToArray());

            return outPath;
        }


        public static void MergeFiles(string destinationFile, string[] sourceFiles)
        {

            try
            {

                byte[] bs = MergePDFs(sourceFiles);
                using (var fsm = new FileStream(destinationFile, FileMode.Create))
                {
                    fsm.Write(bs, 0, bs.Length);
                    fsm.Flush();
                }

            }
            catch (Exception e)
            {
                string strOb = e.Message;
            }
        }
        /// <summary>
        /// 合并多个pdf文件，并返回合并后的文件字节
        /// </summary>
        /// <param name="pdfFiles"></param>
        /// <returns></returns>
        private static byte[] MergePDFs(string[] pdfFiles)
        {
            if (pdfFiles == null || pdfFiles.Length <= 0)
            {
                return null;
            }
            if (pdfFiles.Length == 1)
            {
                return File.ReadAllBytes(pdfFiles[0]);
            }


            PdfReader reader;
            Document document;
            PdfWriter writer;
            MemoryStream msFinalPdf;
            using (msFinalPdf = new MemoryStream())
            {

                reader = new PdfReader(pdfFiles[0]);
                using (document = new Document())
                {
                    //一个PdfSmartCopy基类
                    writer = new PdfSmartCopy(document, msFinalPdf);
                    document.Open();

                    for (int k = 0; k < pdfFiles.Length; k++)
                    {
                        reader = new PdfReader(pdfFiles[k]);
                        //将子文件中的页都追加到尾部
                        for (int i = 1; i < reader.NumberOfPages + 1; i++)
                        {
                            ((PdfSmartCopy)writer).AddPage(writer.GetImportedPage(reader, i));
                        }
                        writer.FreeReader(reader);

                    }
                    reader.Close();
                    writer.Close();
                    document.Close();
                }
            }

            return msFinalPdf.ToArray();
        }


下面的代码合并pdf  就会产生体积增加。字体重复被嵌入的问题

public static void MergeFiles(string destinationFile, string[] sourceFiles)
{

    try
    {
        int f = 0;
        // we create a reader for a certain document
        PdfReader reader = new PdfReader(sourceFiles[f]);
        // we retrieve the total number of pages
        int n = reader.NumberOfPages;
        //Console.WriteLine("There are " + n + " pages in the original file.");
        // step 1: creation of a document-object
        Document document = new Document(reader.GetPageSizeWithRotation(1));
        // step 2: we create a writer that listens to the document
        PdfWriter writer = PdfWriter.GetInstance(document, new FileStream(destinationFile, FileMode.Create));
        // step 3: we open the document
        document.Open();
        PdfContentByte cb = writer.DirectContent;
        PdfImportedPage page;
        int rotation;
        // step 4: we add content
        while (f < sourceFiles.Length)
        {
            int i = 0;
            while (i < n)
            {
                i++;
                document.SetPageSize(reader.GetPageSizeWithRotation(i));
                document.NewPage();
                page = writer.GetImportedPage(reader, i);
                rotation = reader.GetPageRotation(i);
                if (rotation == 90 || rotation == 270)
                {
                    cb.AddTemplate(page, 0, -1f, 1f, 0, 0, reader.GetPageSizeWithRotation(i).Height);
                }
                else
                {
                    cb.AddTemplate(page, 1f, 0, 0, 1f, 0, 0);
                }
                //Console.WriteLine("Processed page " + i);
            }
            f++;
            if (f < sourceFiles.Length)
            {
                reader = new PdfReader(sourceFiles[f]);
                // we retrieve the total number of pages
                n = reader.NumberOfPages;
                //Console.WriteLine("There are " + n + " pages in the original file.");
            }
        }
        // step 5: we close the document
        document.Close();
    }
    catch (Exception e)
    {
        string strOb = e.Message;
    }
}

----下面也会产生重复字体嵌入的----

 public static void Merge(List<String> InFiles, String OutFile)
    {

        using (FileStream stream = new FileStream(OutFile, FileMode.Create))
        using (Document doc = new Document())
        using (PdfCopy pdf = new PdfCopy(doc, stream))
        {
            doc.Open();

            PdfReader reader = null;
            PdfImportedPage page = null;

            //fixed typo
            InFiles.ForEach(file =>
            {
                reader = new PdfReader(file);

                for (int i = 0; i < reader.NumberOfPages; i++)
                {
                    page = pdf.GetImportedPage(reader, i + 1);
                    pdf.AddPage(page);
                }

                pdf.FreeReader(reader);
                reader.Close();
                File.Delete(file);
            });
        }