如果只需要頁碼展示 “第 N 頁”請參照第一個程式碼段內容即可;
如果需要頁碼展示 “第 N 頁 共 Y 頁”, 請參照第二段程式碼段內容.

package com.dhec.checkReport.util;

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

import com.lowagie.text.Document;
import com.lowagie.text.Element;
import com.lowagie.text.ExceptionConverter;
import com.lowagie
 
.text.Font;
import com.lowagie.text.Paragraph;
import com.lowagie.text.pdf.BaseFont;
import com.lowagie.text.pdf.PdfContentByte;
import com.lowagie.text.pdf.PdfPageEventHelper;
import com.lowagie.text.pdf.PdfTemplate;
import com.lowagie.text.pdf.PdfWriter;

public class PdfExport extends PdfPageEventHelper {
    public PdfTemplate tpl;
 

    public BaseFont bf;

    public static void main(String[] args) throws IOException {

        Document document = new Document();
        try {
            PdfWriter writer = PdfWriter.getInstance(document,new FileOutputStream("D:\\aaaa\\checkRepoetAction.pdf"));
            writer.setPageEvent
 
(new PdfExport());

            BaseFont bfChinese = BaseFont.createFont("STSong-Light","UniGB-UCS2-H", BaseFont.NOT_EMBEDDED);

            document.open();

            Paragraph title = new Paragraph("測試內容。。。。", new Font(bfChinese, 15));
            title.setAlignment(Element.ALIGN_CENTER);
            document.add(title);
        } catch (Exception de) {
            de.printStackTrace();
        }
        document.close();
    }



    public void onOpenDocument(PdfWriter writer, Document document) {
        try {
            tpl = writer.getDirectContent().createTemplate(100, 100);
            bf = BaseFont.createFont("STSong-Light", "UniGB-UCS2-H",
                    BaseFont.NOT_EMBEDDED);
        } catch (Exception e) {
            throw new ExceptionConverter(e);
        }
    }

    public void onEndPage(PdfWriter writer, Document document) {
        // 在每頁結束的時候把“第x頁”資訊寫道模版指定位置
        PdfContentByte cb = writer.getDirectContent();
        cb.saveState();
        String text = "第" + writer.getPageNumber() + "頁,共";
        cb.beginText();
        cb.setFontAndSize(bf, 8);
        cb.setTextMatrix(460, 786);// 定位“第x頁,共” 在具體的頁面除錯時候需要更改這xy的座標
        cb.showText(text);
        cb.endText();
        cb.addTemplate(tpl, 492, 786);// 定位“y頁” 在具體的頁面除錯時候需要更改這xy的座標

        cb.saveState();
        cb.stroke();
        cb.restoreState();
        cb.closePath();// sanityCheck();
    }

    public void onCloseDocument(PdfWriter writer, Document document) {
        // 關閉document的時候獲取總頁數，並把總頁數按模版寫道之前預留的位置
        tpl.beginText();
        tpl.setFontAndSize(bf, 8);
        tpl.showText(Integer.toString(writer.getPageNumber() - 1) + "頁");
        tpl.endText();
        tpl.closePath();// sanityCheck();
    }
}

try
          {
            //讀取檔案
            PdfReader pdfReader = new PdfReader("D:\\aaaa\\checkRepoetAction.pdf");

            //生成檔案
            PdfStamper pdfStamper = new PdfStamper(pdfReader, new FileOutputStream("D:\\HelloWorld-modified.pdf"));


            for(int i=1; i<= pdfReader.getNumberOfPages(); i++)
            {
                PdfContentByte content = pdfStamper.getUnderContent(i);
                if(i == pdfReader.getNumberOfPages()){
                    //新增文字
                    BaseFont font = BaseFont.createFont("STSong-Light", "UniGB-UCS2-H",BaseFont.NOT_EMBEDDED);
                    content.beginText();
                    content.setFontAndSize(font, 20);
                    content.setTextMatrix(200, 200);
                    content.showTextAligned(Element.CCITT_ENDOFBLOCK,"第   " + 1 + "  頁\t共   " + 9 + "頁",420,20,0);//左邊距、下邊距
                    content.endText();
                }
            }

            pdfStamper.close();

          } catch (IOException e) {
            e.printStackTrace();
          } catch (DocumentException e) {
            e.printStackTrace();
          }