diff --git a/frontend/src/css/pdf-file-view.css b/frontend/src/css/pdf-file-view.css
index 80c5a05b07..89fac98e25 100644
--- a/frontend/src/css/pdf-file-view.css
+++ b/frontend/src/css/pdf-file-view.css
@@ -1,6 +1,7 @@
 .pdf-file-view {
   overflow: hidden;
   position: relative;
+  z-index: 0;
 }
 
 /* for pdf online file view */