warn you before printing the document : Print « PDF « Java Tutorial

1. Java Tutorial
2. PDF
3. Print

import java.io.FileOutputStream;

import com.lowagie.text.Document;
import com.lowagie.text.Paragraph;
import com.lowagie.text.pdf.PdfAction;
import com.lowagie.text.pdf.PdfContentByte;
import com.lowagie.text.pdf.PdfDestination;
import com.lowagie.text.pdf.PdfWriter;

public class MainClass {
  public static void main(String[] args) throws Exception {
    Document document = new Document();
    PdfWriter writer = PdfWriter.getInstance(document, new FileOutputStream("2.pdf"));
    document.open();

    document.add(new Paragraph("test."));
    PdfAction copyrightNotice = PdfAction.javaScript(
        "app.alert('Warning: this document is protected by copyright.');\r", writer);
    writer.setAdditionalAction(PdfWriter.WILL_PRINT, copyrightNotice);

    
    document.close();
  }
}