<style>
  .back-img {
    background-image: url("http://potosi.bo/wp-content/uploads/2022/11/317075051_503965601769846_6494597033786355730_n.jpg");
    background-repeat: no-repeat;
    background-size: contain;
    height: 788px;
    width: 433px;
    text-align: center;
    padding-top: 300px
  }
  .btn {
    background-color: aqua;
    padding: 15px 25px;
    border: 0px;
  }
</style>
<div class="back-img wp-image-3501">
  <button class="btn  alignnone size-medium wp-image-3501" onclick="window.open('http://potosi.bo/wp-content/uploads/2022/11/programafic2022.pdf', '_blank')"> Descargar </button>
</div>