PDDocument destination = list.get(startPage);
PDFMergerUtility merger = new PDFMergerUtility();
for (int i = startPage + 1; i < endPage; i++) {
PDDocument tmpDocument = list.get(i);
merger.appendDocument(destination, tmpDocument);
}
ByteArrayOutputStream bos = new ByteArrayOutputStream();
COSWriter writer = new COSWriter(bos);