html,
body {
  margin: 0;
  padding: 0;
  height: 100%;
}
#pdf-iframe {
  width: 100%;
  height: 100vh;
  border: none;
}
#fallback-link {
  display: none;
  width: 90%;
  padding: 0.6em;
  background-color: #f9f9f9;
  border: 1px solid #ccc;
  margin: 6em auto;
  line-height: 1.8em;
}
#fallback-link a {
  color: #fff;
  background-color: red;
  padding: 0.3em 0.2em;
  font-weight: bold;
}