chamilo-lms2/main/inc/lib/javascript/ViewerJS/PDFViewerPlugin.css

.page {
    margin: 7px auto 7px auto;
    position: relative;
    overflow: hidden;
    background-clip: content-box;
    background-color: white;
    
    box-shadow:         0px 0px 7px rgba(0, 0, 0, 0.75);
    -webkit-box-shadow: 0px 0px 7px rgba(0, 0, 0, 0.75);
    -moz-box-shadow:    0px 0px 7px rgba(0, 0, 0, 0.75);
    -ms-box-shadow:    0px 0px 7px rgba(0, 0, 0, 0.75);
    -o-box-shadow:    0px 0px 7px rgba(0, 0, 0, 0.75);
}

.textLayer {
  position: absolute;
  left: 0;
  top: 0;
  right: 0;
  bottom: 0;
  color: #000;
  font-family: sans-serif;
  overflow: hidden;
}

.textLayer > div {
  color: transparent;
  position: absolute;
  line-height: 1;
  white-space: pre;
  cursor: text;
}

::selection { background:rgba(0,0,255,0.3); }
::-moz-selection { background:rgba(0,0,255,0.3); }