合并InputStream流

           //将流添加到list
            List<InputStream> list = new ArrayList<InputStream>();
            list.add(iStream);
            list.add(iPutStream);

            //遍历list ,合并流
            Document document = new Document();
            ByteArrayOutputStream out = new ByteArrayOutputStream();
            PdfCopy copy = new PdfCopy(document, out);
            document.open();
            for (InputStream pdf : list) {
                if (pdf == null) {
                    continue;
                }
                copy.addDocument(new PdfReader(pdf));
            }
            document.close();
            //获取合并之后的流
            InputStream inputIs = new ByteArrayInputStream(out.toByteArray());