title: How to solve pdf header signature not found error?
body: <p>I'm using iText in my java program for editing an existing pdf.The generated pdf could not open and it shows pdf header signature not found error.I'm using both my input and output file in a same name.</p>
  
  <pre><code>private static String INPUTFILE = "/sample.pdf";
  private static String OUTPUTFILE = "/sample.pdf";       
  public static void main(String[] args) 
          throws DocumentException,
          IOException 
  {
      Document doc = new Document();
      PdfWriter writer = PdfWriter.getInstance(doc,new FileOutputStream(OUTPUTFILE));
      doc.open();
      PdfReader reader = new PdfReader(INPUTFILE);
      int n;
      n = reader.getNumberOfPages();
      System.out.println("No. of Pages :" +n);
      for (int i = 1; i &lt;= n; i++) 
      {
              if (i == 1)                 
              {            
                     Rectangle rect = new Rectangle(85,650,800,833);
                     PdfFormField pushbutton = PdfFormField.createPushButton(writer);
                     pushbutton.setWidget(rect, PdfAnnotation.HIGHLIGHT_PUSH);
                     PdfContentByte cb = writer.getDirectContent();
                     PdfAppearance app = cb.createAppearance(380,201);
                     app.rectangle(62,100,50,-1);
                     app.fill();
                     pushbutton.setAppearance(PdfAnnotation.APPEARANCE_NORMAL,app);
                     writer.addAnnotation(pushbutton);
                     PdfImportedPage page = writer.getImportedPage(reader, i);
                     Image instance = Image.getInstance(page);
                     doc.add(instance);
                  }
  </code></pre>