the value will be a factor. In this
  case the factor levels describe the possible values for the field. For
  example for a checkbox the typical level names would be "Off" and "Yes",
  corresponding to non checked and checked states respectively.</p>
    <h2 class="hasAnchor" id="references"><a class="anchor" href="#references"></a>References</h2>

    <p><a href='https://www.pdflabs.com/tools/pdftk-the-pdf-toolkit/'>https://www.pdflabs.com/tools/pdftk-the-pdf-toolkit/</a></p>
    <h2 class="hasAnchor" id=