Java合并PDF文档的三种常用方式总结

 <dependency>
     <groupId>org.apache.pdfbox</groupId>
     <artifactId>pdfbox</artifactId>
     <version>2.0.26</version>
 </dependency>

// 添加待合并文件
for (ZipUtil.RelativeFile sourcePdf : fileRefers) {
   long time1 = System.currentTimeMillis();
   log.info("开始添加{}， 大小：{}MB, 路径：{}", (++index),
   FileUtils.newFile(sourcePdf.getFilePath()).length() / 1024 / 1024, sourcePdf.getFilePath());
   try (PDDocument document = PDDocument.load(FileUtils.newFile(sourcePdf.getFilePath()), MemoryUsageSetting.setupTempFileOnly());
        ) {
            // 页面大纲（1级）
            String newName = FileUtils.newFile(sourcePdf.getRelativePath()).getName();
            newName = StringUtils.trimToEmpty(newName).replace("." + FilenameUtils.getExtension(newName), "");
            PdfBoxBookmark boxData = new PdfBoxBookmark(newName, totalPage);

            PDDocumentOutline outline = document.getDocumentCatalog().getDocumentOutline();
            if (outline != null) {
                buildBookMark(outline, boxData, totalPage);
            }
            /
            allBookList.add(boxData);

            mergePdf.addSource(sourcePdf.getFilePath());

            // 更新总页码
            totalPage += document.getNumberOfPages();
        } catch (IOException e) {
            e.printStackTrace();
            log.error("合并pdf失败:{}",e);
            throw new BaseException("文件不存在：" + sourcePdf.getFilePath());
        }
        log.info("结束添加，添加后，总{}页：{},耗费：{}秒",totalPage,
                sourcePdf.getFilePath(), (System.currentTimeMillis() - time1) / 1000);
    }

    // 设置合并后的pdf文件路径
    mergePdf.setDestinationFileName(destFilePath);

    // 合并pdf
    try {
        mergePdf.setDocumentMergeMode(PDFMergerUtility.DocumentMergeMode.OPTIMIZE_RESOURCES_MODE);
        mergePdf.mergeDocuments(MemoryUsageSetting.setupTempFileOnly());
    } catch (IOException e) {
        e.printStackTrace();
        throw new BaseException("合并发生异常");
    }

<dependency>
    <groupId>e-iceblue</groupId>
    <artifactId>spire.pdf</artifactId>
    <version>9.5.6</version>
</dependency>

String[] files = new String[] {
                "C:\\Users\\test\\Desktop\\tmp\\001\\20241014-001\\error-file.pdf",
                "C:\\Users\\test\\Desktop\\tmp\\001\\20241014-001\\111.pdf"};

//Merge documents and return an object of PdfDocumentBase
PdfDocumentBase pdf = PdfDocument.mergeFiles(files);

//Save the result to a PDF file
pdf.save("C:\\Users\\test\\Desktop\\tmp\\001\\20241014-001\\MergedPDF222.pdf", FileFormat.PDF);

<dependency>
    <groupId>com.itextpdf</groupId>
    <artifactId>itextpdf</artifactId>
    <version>5.5.13.4</version>
</dependency>

String[] pdfs = new String[] {
                "C:\\Users\\test\\Desktop\\tmp\\001\\20241014-001\\0001.pdf",
                "C:\\Users\\test\\Desktop\\tmp\\001\\20241014-001\\0002.pdf"};

String outputPdf = "C:\\Users\\test\\Desktop\\tmp\\001\\20241014-001\\MergedPDF333-.pdf"; // 合并后的PDF文件

try {
    Document document = new Document();
    PdfCopy copy = new PdfCopy(document, new FileOutputStream(outputPdf));
    document.open();

    for (String pdf : pdfs) {
        PdfReader reader = new PdfReader(pdf);
        for (int i = 1; i <= reader.getNumberOfPages(); i++) {
            document.newPage();
            copy.addPage(copy.getImportedPage(reader, i));
        }
        reader.close();
    }

    document.close();
    System.out.println("PDFs merged successfully.");
} catch (Exception e) {
    e.printStackTrace();
}