title: How can I add a underline of header of pdf by using itext ColumnText? I set the width of line 100%, but it doesn't work
body: <pre><code>//set the width to 90%, but the generated pdf shows 100%. Please look at the picture below
  LineSeparator underLine = new LineSeparator(1, 90f, null, Element.ALIGN_CENTER, 0);
  Phrase phrase1 = new Phrase();
  phrase1.add(underLine);
  ColumnText.showTextAligned(writer.getDirectContent(), Element.ALIGN_CENTER, phrase1, 0, pageSize.getHeight() - 75, 0);
  </code></pre>
  
  <p>whatever I set 90% or 100% for the width, it shows 100%.Please look at the picture below</p>
  
  <p><img src="https://i.stack.imgur.com/QwCSq.png" alt="the screenshot of generated pdf"></p>