<!-- here we call the function that makes PDF -->
<div class="container">
    <div class="row">

        <div class="col-sm-3 align-self-center">
            <button id="bt_add" class="btn btn-default">Agregar</button>
        </div>

        <div class="col-sm-3 align-self-center">
            <button id="bt_add" class="btn btn-default">Calcular</button>
        </div>

        <div class="col-sm-3 align-self-center">
            <button  class="btn btn-default"  onclick="HTMLtoPDF()">Download PDF</button>
        </div>

        <form action="guardarArchivos.php" method="post" enctype="multipart/form-data">
        <div class="col-sm-3 align-self-center">
            <button class="btn btn-default" name="boton_guarda" value="Guardar en disco" onclick="javascript:document.execCommand('SaveAs','true','tu_archivo.txt')">Guardar</button>
        </div>
        </form>


    </div>
</div>


<!-- these js files are used for making PDF -->
<script src="js/jspdf.js"></script>
<script src="js/jquery-2.1.3.js"></script>
<script src="js/pdfFromHTML.js"></script>
<script src="https://code.jquery.com/jquery-3.3.1.slim.min.js" integrity="sha384-q8i/X+965DzO0rT7abK41JStQIAqVgRVzpbzo5smXKp4YfRvH+8abtTE1Pi6jizo" crossorigin="anonymous"></script>