<dependency>
            <groupId>com.itextpdf</groupId>
            <artifactId>itextpdf</artifactId>
            <version>5.5.13</version>
        </dependency>

import com.itextpdf.text.Document;
import com.itextpdf.text.DocumentException;
import com.itextpdf.text.pdf.PdfCopy;
import com.itextpdf.text.pdf.PdfImportedPage;
import com.itextpdf.text.pdf.PdfReader;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

public class Split2 {
    public static void main(String[] args) {
        String inputFile= "C:\\1.pdf";
        splitFile(inputFile,1,1);//第1页为一个文件
        splitFile(inputFile,2,2);//第2页为一个文件
        splitFile(inputFile,3,4);//第3，4页为一个文件
        splitFile(inputFile,5,8);//以下类似
        splitFile(inputFile,9,12);
        splitFile(inputFile,13,13);
        splitFile(inputFile,14,18);
    }

    public static String splitFile(String pdfFile,Integer from,Integer end){

        Document document = null;
        PdfCopy copy = null;
        try {
            PdfReader reader = new PdfReader(pdfFile);
            int n = reader.getNumberOfPages();
            if(end==0){
                end = n;
            }
            List<String> savepaths = new ArrayList<String>();
            int a = pdfFile.lastIndexOf(".pdf");
            String staticpath = pdfFile.substring(0, a);
            String savepath = staticpath+ "_from_"+from+"_to_"+end+"_.pdf";
            savepaths.add(savepath);
            document = new Document(reader.getPageSize(1));
            copy = new PdfCopy(document, new FileOutputStream(savepaths.get(0)));
            document.open();
            for(int j=from; j<=end; j++) {
                document.newPage();
                PdfImportedPage page = copy.getImportedPage(reader, j);
                copy.addPage(page);
            }
            document.close();
            return new File(savepath).getName();
        } catch (IOException e) {
            return null;
        } catch(DocumentException e) {
            return null;
        }
    }

}