输入一个数字截取pdf里的内容后几页放到另一个pdf文件

package com.pdf;

import java.io.FileOutputStream;
import java.io.IOException;

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;

public class PdfContent {
/**
* @param args
* @throws IOException
* @throws DocumentException
*/
public static void copyPdf(String sourceFile ,String targetFile, int cutpagetotal)throws Exception{
Document doc = new Document();
try {
PdfReader pdfReader = new PdfReader(sourceFile);
PdfCopy pdfCopy = new PdfCopy(doc, new FileOutputStream(
targetFile));
PdfImportedPage impPage = null;
doc.open();
int allPageNum=pdfReader.getNumberOfPages();
if(cutpagetotal>allPageNum){
cutpagetotal=allPageNum;
}
for (int i = pdfReader.getNumberOfPages(); i > allPageNum- cutpagetotal; i--) {
impPage = pdfCopy.getImportedPage(pdfReader,allPageNum-cutpagetotal+allPageNum-i+1);
pdfCopy.addPage(impPage);
}
} catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
}
finally{
doc.close();
}
}
public static void main(String[] args) throws Exception {

copyPdf("C:\\Users\\jiangjun\\Desktop\\文档包\\IDL-ETD 3.0系统安装说明.pdf", "C:\\Users\\jiangjun\\Desktop\\IDL-ETD 3.0系统安装说明.pdf", 3);

}
}