JSFiddle - React, Tailwind, and code Playground

HTML

<div id="div-text">
      <div id="shouldBeOnTop">my text that should be on top</div>
</div>
<div id="div-frame">
    <iframe src="http://legallo1.free.fr/french/CV_JLG.pdf" width="100%" height="200px"/>
</div>

CSS

#div-text{
    position:relative;
    left:210px;
    top:20px
}

#shouldBeOnTop{
    position:relative;
    right:60px;
    background-color:red;
    width:100px;
    z-index:-2000;
}

#div-frame{
    position:relative;
     z-index:100;
}