C#实现多个PDF合并及去除文字水印功能

实现pdf合并就是使用Spire.Pdf.dll类库的方法，但是注意需要同时引用Spire.Pdf.dll和Spire.License.dll两个类库，且两个类库的版本要一致

 String[] files = new String[Dir.GetFiles().Length];
                int i = 0;
                foreach (FileInfo f in Dir.GetFiles()) //循环文件
                {
                    files[i] = f.FullName;
                    i = i + 1;
                }
 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

但是使用spire的话合并成的pdf第一页会出现文字水印，这并不是我们要的，所以需要去除这个文字水印，那么就要用到iTextSharp.text.pdf.dll类库

 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(1);//获取第一页
            contentarray = page.GetAsArray(PdfName.CONTENTS);
            if (contentarray != null)
            {
                //Loop through content
                for (int j = 0; 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") >= 0 || content.IndexOf(watermarkText) >= 0)//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();
            }

对，就是这么简单