code: public Chunk setUnderline(float thickness, float yPosition) {
  		return setUnderline(null, thickness, 0f, yPosition, 0f,
  				PdfContentByte.LINE_CAP_BUTT);
  	}
docs: Sets an horizontal line that can be an underline or a strikethrough.
  Actually, the line can be anywhere vertically and has always the <CODE>
  Chunk</CODE> width. Multiple call to this method will produce multiple
  lines.
  
  @param thickness
  the absolute thickness of the line
  @param yPosition
  the absolute y position relative to the baseline
  @return this <CODE>Chunk</CODE>