最近一直找发票合并的小工具，没想到这玩意儿还收费，想着就自己用pdfbox的库弄一个。最终效果如图:

1.maven依赖

 
        
            org.apache.pdfbox
            pdfbox
            2.0.24
        
        
            org.projectlombok
            lombok
            1.16.10
        
        
            cn.hutool
            hutool-all
            5.5.7
        

 2.合并代码

           网上绝大多数都是多个PDF文件合并成一个文件，每个PDF是单独的页面。想两张合成一张放到一个页面就只能自己改造了。

多文件合并成多页：

public static void mergeDocument(String path) throws Exception {
        File file = new File(path);
        if (file.isDirectory()){
            PDFMergerUtility merger = new PDFMergerUtility();
            File[] files = file.listFiles();
            for (File tmp: files){
                System.out.println(tmp.getAbsolutePath());
                merger.addSource(tmp);
            }
            String out = path + File.separator + DateUtil.format(new Date(), DatePattern.PURE_DATETIME_PATTERN) + "合并发票.pdf";
            merger.setDestinationFileName(out);
            merger.mergeDocuments(MemoryUsageSetting.setupMainMemoryOnly());
        }
    }

多文件合成单页两张:

public class Reader {
    /**
     * 计算发票金额
     * @param tmp
     * @return
     */
    @SneakyThrows
    public static BigDecimal summary(File tmp) {
        PDDocument doc = PDDocument.load(tmp);
        //创建检索对象
        PDFTextStripper pdfStripper = new PDFTextStripper();
        String content = pdfStripper.getText(doc);
        doc.close();
        Pattern pattern = Pattern.compile("[¥￥]\\s*\\d+\\.\\d{2}");
        Matcher matcher = pattern.matcher(content);
        List amountList = new ArrayList<>();
        String str = "";
        while (matcher.find()){
            str = matcher.group();
            String amountStr = str.replaceAll("[¥￥]\\s*", "");
            amountList.add(new BigDecimal(amountStr));
        }
        System.out.println(tmp.getName() +","+ str);
        Collections.sort(amountList);
        return amountList.get(amountList.size()-1);
    }
}

public class Test {
    /**
     * 文件列表
     * @param path
     * @return
     */
    public static List fileList(String path){
        List result = new ArrayList();
        File file = new File(path);
        if (file.isDirectory()){
            File[] files = file.listFiles();
            BigDecimal sum = BigDecimal.ZERO;
            for (File tmp: files){
                if (!tmp.getName().startsWith("test")){
                    result.add(tmp.getAbsolutePath());
                    BigDecimal ele = Reader.summary(tmp);
                    sum = sum.add(ele);
                }
            }
            System.out.println("总金额:¥ "+sum.toPlainString());
        }
        return result;
    }
    public static void main(String[] args) throws Exception {
        String path = "E:\\文档\\发票\\test\\test_"+ DateUtil.format(new Date(), "yyyyMMdd_HHmmss")+".pdf";
        //创建空白文档
        PDDocument document = new PDDocument();
        //布局
        LayerUtility layerUtility = new LayerUtility(document);
        //添加文档
        List files = fileList("E:\\文档\\发票\\test");
        //缩放比例
        float scaleX = 0.95f;
        float scaleY = 0.95f;
        //创建空白页面
        PDPage blankPage = new PDPage();
        document.addPage(blankPage);
        PDRectangle rectangle = blankPage.getMediaBox();
        float height = rectangle.getHeight();
        float width = rectangle.getWidth();
        for (int i=0;i 
说明下，这个PDF的文档坐标是左下角是原点坐标，向右X轴增加，向上Y轴增加。