.iframe_wrap{
  position: relative;
  width: 100%;
  aspect-ratio: 16 / 9;   /* 원하는 비율로 변경 */
  overflow: hidden;
}
.iframe_wrap iframe{
  position: absolute;
  width: 100%;
  height: 100%;
  border: 0;
}
.pdfviewer {
	margin:1% 0;
	border:1px solid #aaa;
	height:1400px;
	width:990px;
}
@media (max-width:767px){ 
	.pdfviewer { 
		height:350px;
	}
}