使用 openPDF 创建带目录的文档时候, 使用如下方式, 可以保证目录页码准确

public static void main(String[] args) throws Exception {
	pdfboxTest5();
}

private static void pdfboxTest5() throws DocumentException, IOException {
	File file = new File("E:\\sss\\test5.pdf");
	Document doc = new Document(PageSize.A4);
	String tempFileName = "." + File.separator + UUID.randomUUID().toString() + ".pdf";
	PdfWriter pdfWriter = PdfWriter.getInstance(doc, new FileOutputStream(new File(tempFileName)));
	ContentEvent contentEvent = new ContentEvent();
	pdfWriter.setPageEvent(contentEvent);
	List<Chapter> chapterList = new ArrayList<>();
	HeaderFooter header = new HeaderFooter(false, new Phrase("测试页眉", getFont(100)));
	header.setBorder(Rectangle.BOTTOM);
	header.setAlignment(Element.ALIGN_CENTER);
	HeaderFooter footer = new HeaderFooter(new Phrase("第", getFont(100)), new Phrase("页", getFont(100)));
	footer.setBorder(Rectangle.TOP);
	footer.setAlignment(Element.ALIGN_CENTER);
	doc.setHeader(header);
	doc.setFooter(footer);

	doc.open();
	for (int i = 0; i < 10; i++) {
		Chapter chapter = new Chapter(new Paragraph("第" + (i + 1) + "单元", getFont(1)), i + 1);
		chapter.setTriggerNewPage(false);
//		chapter.setIndentation(10);
		for (int j = 0; j < 5; j++) {
			Section section = chapter.addSection(10, new Paragraph("第" + (j + 1) + "节", getFont(2)));
			for (int k = 0; k < 3; k++) {
				Section subSection = section.addSection(10, new Paragraph("第" + (k + 1) + "题", getFont(3)));
				subSection.add(new Paragraph("测试测试测试测试测试测试测试测试测试测试测试测试测试测试测试测试测试测试测试测试测试测试测试测试测测试测试", getFont(100)));
			}
		}
		chapterList.add(chapter);
		doc.add(chapter);
	}
	doc.close();

	PdfReader reader = new PdfReader(tempFileName);
	int numberOfPages = reader.getNumberOfPages();
	PdfTextExtractor pdfTextExtractor = new PdfTextExtractor(reader);
	Map<String, Integer> muluTempMap = new LinkedHashMap<>();
	for (int i = 0; i < numberOfPages; i++) {
		String textFromPage = pdfTextExtractor.getTextFromPage(i + 1);
		String[] texts = Arrays.stream(textFromPage.split("\n")).map(string -> string.trim()).filter(string -> string.trim().indexOf(".") >= 1 && string.trim().contains(". ")).toArray(String[]::new);
		for (String string : texts) {
			muluTempMap.put(string.trim(), i + 1);
		}
	}
	new File(tempFileName).delete();

	Document document = new Document(PageSize.A4);
	PdfWriter.getInstance(document, new FileOutputStream(file));
	document.open();
	Paragraph mulu = new Paragraph("目录", getFont(1));
	mulu.setSpacingAfter(10);
	Chapter indexChapter = new Chapter(mulu, 0);
	indexChapter.setNumberDepth(0);
	for (Entry<String, Integer> entry : contentEvent.index.entrySet()) {
		String title = entry.getKey();
		String titleSub = title.substring(0, title.indexOf(". ") + 1);
		String titleTemp = titleSub.replaceAll("\\.", "");
		Paragraph paragraph = new Paragraph(title, getFont(titleSub.length() - titleTemp.length() + 10));
		paragraph.setIndentationLeft((titleSub.length() - titleTemp.length() - 1) * 10);
		paragraph.add(new Chunk(new DottedLineSeparator()));
		paragraph.add(new Chunk(String.valueOf(muluTempMap.get(entry.getKey())), getFont(100)));
		indexChapter.add(paragraph);
	}

	document.add(indexChapter);
	document.setHeader(header);
	document.setFooter(footer);
	document.resetPageCount();
	document.newPage();
	for (Chapter chapter : chapterList) {
		document.add(chapter);
	}
	document.close();
}

private static class ContentEvent extends PdfPageEventHelper {
	Map<String, Integer> index = new LinkedHashMap<>();

	@Override
	public void onChapter(PdfWriter writer, Document document, float paragraphPosition, Paragraph title) {
		index.put(title.getContent().trim(), 0);
	}

	@Override
	public void onSection(PdfWriter writer, Document document, float paragraphPosition, int depth, Paragraph title) {
		index.put(title.getContent().trim(), 0);
	}
}