合并pdf文档后的IText字符串替换

Question

我正在努力在合并文档后替换文本。我有一个文档是通过IText从头开始创建的。在第一个pdf中，我可以随时替换任何文本。字符串替换的代码如下。

    URL    resource       = CobAccountOpeningLetterFieldServiceTest.class.getResource(SAMPLE_GENERATED_DOCUMENT);
    Date   date           = CobModelUtils.getUtilDateFromString("Nov 02, 2017");
    String region         = "en";
    String dateFromLocale = getDateFromLocale(region, date);

    PdfReader     reader = new PdfReader(resource);
    PdfDictionary dict   = reader.getPageN(1);
    PdfObject     object = dict.getDirectObject(PdfName.CONTENTS);
    if (object instanceof PRStream) {
        PRStream stream     = (PRStream) object;
        byte[]   data       = PdfReader.getStreamBytes(stream);
        String   dataString = new String(data, CHARACTER_ENCODING_SET);
        System.out.println(dataString);
        dataString = dataString.replace(TEMPORARY_DATE_PLACE_HOLDER, dateFromLocale);
        stream.setData(dataString.getBytes(CHARACTER_ENCODING_SET));
    }
    PdfStamper stamper = new PdfStamper(reader, new FileOutputStream(RESULT4));
    stamper.close();
    reader.close();

这个单独工作正常，但是当我合并其中的任何其他文档时，字符串替换将停止处理新PDF。

合并pdf的代码是

private InputStream mergeDocument(List<InputStream> documentToMerge) throws DocumentException, IOException {
    ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
    Document              document              = new Document();
    PdfWriter             pdfWriter             = PdfWriter.getInstance(document, byteArrayOutputStream);
    document.open();
    PdfContentByte cb = pdfWriter.getDirectContent();
    for (InputStream inputStream : documentToMerge) {
        PdfReader pdfReader = new PdfReader(inputStream);
        PdfReader.unethicalreading = true;
        for (int pageOfCurrentReaderPDF = 1; pageOfCurrentReaderPDF <= pdfReader.getNumberOfPages(); pageOfCurrentReaderPDF++) {
            Rectangle r = pdfReader.getPageSize(pdfReader.getPageN(pageOfCurrentReaderPDF));
            document.setPageSize(r);
            document.newPage();
            PdfImportedPage page = pdfWriter.getImportedPage(pdfReader, pageOfCurrentReaderPDF);
            cb.addTemplate(page, 0, 0);
        }
    }
    byteArrayOutputStream.flush();
    document.close();
    return new ByteArrayInputStream(byteArrayOutputStream.toByteArray());
}

任何人都早先遇到过这个问题。请指导，谢谢，