import java.io.FileOutputStream;
import com.lowagie.text.Document;
import com.lowagie.text.PageSize;
import com.lowagie.text.Paragraph;
import com.lowagie.text.pdf.PdfReader;
import com.lowagie.text.pdf.PdfStamper;
import com.lowagie.text.pdf.PdfWriter;
public class MainClass {
public static void main(String[] args) throws Exception {
Document document = new Document(PageSize.A6);
PdfWriter.getInstance(document, new FileOutputStream("2.pdf"));
document.open();
document.add(new Paragraph("Hello World"));
document.add(new Paragraph("Hello People"));
document.close();
PdfReader reader = new PdfReader("2.pdf");
byte[] streamBytes = reader.getPageContent(1);
String contentStream = new String(streamBytes);
System.out.println(contentStream);
StringBuffer buf = new StringBuffer();
int pos = contentStream.indexOf("Hello World") + 11;
buf.append(contentStream.substring(0, pos));
buf.append(", Hello ");
buf.append(contentStream.substring(pos));
String hackedContentStream = buf.toString();
PdfStamper stamper = new PdfStamper(reader, new FileOutputStream("HelloWorldStreamHack.pdf"));
reader.setPageContent(1, hackedContentStream.getBytes());
stamper.close();
}
}