diff --git a/customize.dist/src/less2/include/modals-ui-elements.less b/customize.dist/src/less2/include/modals-ui-elements.less
index 3e449d495..94ec06cc0 100644
--- a/customize.dist/src/less2/include/modals-ui-elements.less
+++ b/customize.dist/src/less2/include/modals-ui-elements.less
@@ -275,8 +275,14 @@
     }
     #cp-upload-preview-container {
         max-width: 100%;
+        max-height: 300px;
+        overflow: auto;
         media-tag {
             max-width: 100%;
+            iframe {
+                // pdfs don't take the full width unless we tell them to
+                width: 100%;
+            }
             & > * {
                 max-width: 100%;
             }