1. 将2个pdf 文档合并成一个

<dependency>
    <groupId>com.itextpdf</groupId>
    <artifactId>itext7-core</artifactId>
    <version>7.1.16</version>
    <type>pom</type>
</dependency>

public class CE06E04Combine {
    private static final String FILE_NAME1 = "src/main/resources/pdf/A.pdf";
    private static final String FILE_NAME2 = "src/main/resources/pdf/B.pdf";
    private static final String DEST = "results/chapter06/AB.pdf";

    public static void main(String[] args) throws IOException {
        CE06E04Combine ce06E04Combine = new CE06E04Combine();
        ce06E04Combine.combinePDF(FILE_NAME1, FILE_NAME2,DEST);
        //ce06E04Combine.combinePDF(FILE_NAME1, FILE_NAME2);
    }

    /**
     * 合并2个文档
     * @param fileName1
     * @param fileName2
     * @return
     */
    private void combinePDF(String fileName1,String fileName2){
        String desFileName = new File(fileName1).getParentFile().getAbsolutePath()+"/" + UUID.randomUUID()+".pdf";
        combinePDF(fileName1,fileName2,desFileName);
    }
    private void combinePDF(String fileName1, String fileName2, String desFileName)  {
        PdfDocument pdf = null;
        try {
            pdf = new PdfDocument(new PdfWriter(desFileName));
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
        //定义合并文档
        PdfMerger merger = new PdfMerger(pdf);
        //添加第一个文档
        PdfDocument firstSourcePdf = null;
        try {
            firstSourcePdf = new PdfDocument(new PdfReader(fileName1));
        } catch (IOException e) {
            e.printStackTrace();
        }
        merger.merge(firstSourcePdf, 1, firstSourcePdf.getNumberOfPages());
        //添加第二个文档
        PdfDocument secondSourcePdf = null;
        try {
            secondSourcePdf = new PdfDocument(new PdfReader(fileName2));
        } catch (IOException e) {
            e.printStackTrace();
        }

        merger.merge(secondSourcePdf, 1, secondSourcePdf.getNumberOfPages());

        // 合并并关闭
        merger.close();
        firstSourcePdf.close();
        secondSourcePdf.close();
        pdf.close();
    }
}

2. 分割文件

public class CE06E04Spliter {
    //要分割的文件
    private static final String FILE_NAME = "src/main/resources/pdf/A.pdf";
    //分割文件存放的位置
    private static final String DEST = "results/chapter06/";

    public static void main(String[] args) throws IOException {
        CE06E04Spliter ce06E04Spliter = new CE06E04Spliter();
       // ce06E04Spliter.pdfSplitter(FILE_NAME1,10,DEST);
        //ce06E04Spliter.pdfSplitter(FILE_NAME,10);
        ce06E04Spliter.pdfSplitter(FILE_NAME,1,8);
    }

    /**
     * 在指定目录等分pdf
     * @param fileName  要分割的文档
     * @param pageNum   分割尺寸
     * @param desDir    分割后存储路径
     * @throws IOException
     */
    private void pdfSplitter(String fileName,Integer pageNum,String desDir) throws IOException {
        PdfReader pdfReader = new PdfReader(fileName);
        PdfDocument pdf = new PdfDocument(pdfReader);
        String name;
        PdfWriter pdfWriter=null;
        PdfDocument pdfWriterDoc = null;
        for (int i = 1; i <= pdf.getNumberOfPages() ; i +=  pageNum) {
            name = desDir+"/"+i+".pdf";
            pdfWriter = new PdfWriter(name);
            pdfWriterDoc = new PdfDocument(pdfWriter);
            int start = i;
            int end = Math.min((start + pageNum-1), pdf.getNumberOfPages());
            //从页数第一页开始，
            pdf.copyPagesTo(start,end,pdfWriterDoc);
        }
        //关闭
        pdfWriterDoc.close();
        pdfWriter.close();
        pdf.close();
        pdfReader.close();
    }

    /**
     * 分割文档，分割后文仔默认存储在原来的文档路径下。
     * @param fileName
     * @param pageNum
     * @throws IOException
     */
    private void pdfSplitter(String  fileName,Integer pageNum) throws IOException {
        String desDir = new File(fileName).getParentFile().getAbsolutePath();
        pdfSplitter(fileName,pageNum,desDir);
    }

    /**
     * 返回自定义片段大小的文件，UUID名称命名。
     * @param fileName
     * @param startPage
     * @param endPage
     * @throws IOException
     */
    public void pdfSplitter(String fileName,int startPage, int endPage) throws IOException {
        //源文档
        PdfReader pdfReader = new PdfReader(fileName);
        PdfDocument pdf = new PdfDocument(pdfReader);
        //目标文档名
        String desDir = new File(fileName).getParentFile().getAbsolutePath()
                +"/"+UUID.randomUUID().toString()+".pdf";
        //生成目标文档
        PdfWriter pdfWriter = new PdfWriter(desDir);
        PdfDocument outPdfDocument = new PdfDocument(pdfWriter);
        //核心代码其实就这一行
        pdf.copyPagesTo(startPage,endPage,outPdfDocument);
        //关闭
        outPdfDocument.close();
        pdfWriter.close();
        pdf.close();
        pdfReader.close();
    }
}

下一步研究一下PDF 转word。

再也不用怕文档太大太占内存了。