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

import com.lowagie.text.*;
import com.lowagie.text.pdf.PdfWriter;

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello World");
        Document document = new Document();
        try {
            PdfWriter.getInstance(document,
                    new FileOutputStream("HelloWorld.pdf"));
            document.open();
            document.add(new Paragraph("Hello World"));
        } 
        catch (DocumentException de) {
            System.err.println(de.getMessage());
        } 
        catch (IOException ioe) {
            System.err.println(ioe.getMessage());
        }
        document.close();
    }
}

import java.io.FileOutputStream;
import java.util.HashMap;

import com.lowagie.text.Element;
import com.lowagie.text.Image;
import com.lowagie.text.PageSize;
import com.lowagie.text.pdf.BaseFont;
import com.lowagie.text.pdf.PdfContentByte;
import com.lowagie.text.pdf.PdfReader;
import com.lowagie.text.pdf.PdfStamper;

public class AddWatermarkPageNumbers {
    public static void main(String[] args) {
        System.out.println("Add watermarks and pagenumbers");
        try {
            PdfReader reader = new PdfReader("ChapterSection.pdf");
            int n = reader.getNumberOfPages();
            // create a stamper that will copy the document to a new file
            PdfStamper stamp = new PdfStamper(reader, 
               new FileOutputStream("watermark_pagenumbers.pdf"));
            // adding some metadata
            HashMap moreInfo = new HashMap();
            moreInfo.put("Author", "Bruno Lowagie");
            stamp.setMoreInfo(moreInfo);
            // adding content to each page
            int i = 0;
            PdfContentByte under;
            PdfContentByte over;
            Image img = Image.getInstance("watermark.jpg");
            BaseFont bf = 
               BaseFont.createFont
                 (BaseFont.HELVETICA, BaseFont.WINANSI, BaseFont.EMBEDDED);
            img.setAbsolutePosition(200, 400);
            while (i < n) {
                i++;
                // watermark under the existing page
                under = stamp.getUnderContent(i);
                under.addImage(img);
                // text over the existing page
                over = stamp.getOverContent(i);
                over.beginText();
                over.setFontAndSize(bf, 18);
                over.setTextMatrix(30, 30);
                over.showText("page " + i);
                over.setFontAndSize(bf, 32);
                over.showTextAligned
                   (Element.ALIGN_LEFT, "DUPLICATE", 230, 430, 45);
                over.endText();
            }
            // adding an extra page
            stamp.insertPage(1, PageSize.A4);
            over = stamp.getOverContent(1);
            over.beginText();
            over.setFontAndSize(bf, 18);
            over.showTextAligned(Element.ALIGN_LEFT, 
                    "DUPLICATE OF AN EXISTING PDF DOCUMENT", 30, 600, 0);
            over.endText();
            // adding a page from another document
            PdfReader reader2 = new PdfReader("SimpleAnnotations1.pdf");
            under = stamp.getUnderContent(1);
            under.addTemplate
                (stamp.getImportedPage(reader2, 3), 1, 0, 0, 1, 0, 0);
            // closing PdfStamper will generate the new PDF file
            stamp.close();
        }
        catch (Exception de) {
            de.printStackTrace();
        }
    }
}