Most of the files are

  <li>JSignPdf: © Josef Cacek - License <a class="reference external" href="http://www.mozilla.org/MPL">MPL</a> or <a class="reference external" href="http://www.gnu.org/licenses/old-licenses/lgpl-2.0.html">LGPL2</a> - <a class="reference external" href="http://jsignpdf.sourceforge.net/">http://jsignpdf.sourceforge.net/</a></li>
  Copyright 2015 Tecnativa - Antonio Espinosa
  Copyright 2017 Tecnativa - Pedro M. Baeza
  Copyright 2018 Tecnativa - David Vidal
  Copyright 2018 Flectra Community

Many files also contain contributions from third
parties. In this case the original copyright of
the contributions can be traced through the
history of the source version control system.

When that is not the case, the files contain a prominent
notice stating the original copyright and applicable
license, or come with their own dedicated COPYRIGHT
and/or LICENSE file.