String[] files = new String[Dir.GetFiles().Length];

                int i = ;

                foreach (FileInfo f in Dir.GetFiles()) //循环文件

                {

                    files[i] = f.FullName;

                    i = i + ;

                }

 string outputFile = newPathDir + "\\" + Dir.Name+".pdf";//输出的路径

                    PdfDocumentBase doc =Spire.Pdf.PdfDocument.MergeFiles(files);

                    doc.Save(outputFile, FileFormat.PDF);

                    //System.Diagnostics.Process.Start(outputFile);//打开文件

 PRStream stream;

            String content;

            PdfArray contentarray;

            string watermarkText = "要去除的水印文字";

            PdfReader reader2 = new PdfReader(path);

            reader2.RemoveUnusedObjects();

            PdfDictionary page = reader2.GetPageN();//获取第一页

            contentarray = page.GetAsArray(PdfName.CONTENTS);

            if (contentarray != null)

            {

                //Loop through content

                for (int j = ; j < contentarray.Size; j++)

                {

                    //Get the raw byte stream

                    stream = (PRStream)contentarray.GetAsStream(j);

                    //Convert to a string. NOTE, you might need a different encoding here

                    content = System.Text.Encoding.ASCII.GetString(PdfReader.GetStreamBytes(stream));//获取pdf页内的文字内容

                    //Look for the OCG token in the stream as well as our watermarked text

                    if (content.IndexOf("/OC") >=  || content.IndexOf(watermarkText) >= )//如果pdf内容包含水印文字

                    {

                        //Remove it by giving it zero length and zero data

                        content= content.Replace(watermarkText, "");//替换水印文字为空

                        byte[] byteArray = System.Text.Encoding.Default.GetBytes(content);//转换为byte[]

                        stream.Put(PdfName.LENGTH, new PdfNumber(byteArray.Length));//重新指定大小

                        stream.SetData(byteArray);//重新赋值

                    }

                }

            }

            FileStream fs = new FileStream(outputFile, FileMode.Create, FileAccess.Write, FileShare.None);

            PdfStamper stamper = new PdfStamper(reader2, fs);

            //stamper.SetFullCompression();

            if (stamper != null) {

                stamper.Close();

            }

            if (null != fs)

            {

                fs.Close();

            }

            if (null != reader2)

            {

                reader2.Close();

            }