diff --git a/app/assets/javascripts/pdfjs_viewer/viewer.js b/app/assets/javascripts/pdfjs_viewer/viewer.js
index f53c073f..64a8354d 100644
--- a/app/assets/javascripts/pdfjs_viewer/viewer.js
+++ b/app/assets/javascripts/pdfjs_viewer/viewer.js
@@ -1886,7 +1886,7 @@ var PDFViewerApplication = {
 };
 var validateFileURL = void 0;
 {
-  var HOSTED_VIEWER_ORIGINS = ['null', 'http://mozilla.github.io', 'https://mozilla.github.io'];
+  var HOSTED_VIEWER_ORIGINS = window.HOSTED_VIEWER_ORIGINS || ['null', 'http://mozilla.github.io', 'https://mozilla.github.io'];
   validateFileURL = function validateFileURL(file) {
     if (file === undefined) {
       return;
diff --git a/app/views/pdfjs_viewer/viewer/_before_load.html.erb b/app/views/pdfjs_viewer/viewer/_before_load.html.erb
new file mode 100644
index 00000000..695b5bcd
--- /dev/null
+++ b/app/views/pdfjs_viewer/viewer/_before_load.html.erb
@@ -0,0 +1 @@
+<!-- Touch file app/views/pdfjs_viewer/viewer/_before_load.html.erb to add extra head data before pdfjs loads. -->
diff --git a/app/views/pdfjs_viewer/viewer/_head.html.erb b/app/views/pdfjs_viewer/viewer/_head.html.erb
index 5eb35561..dc6f6190 100644
--- a/app/views/pdfjs_viewer/viewer/_head.html.erb
+++ b/app/views/pdfjs_viewer/viewer/_head.html.erb
@@ -1,6 +1,8 @@
 <meta name="pdfjs_viewer_verbosity" content="<%= ENV.fetch("PDFJS_VIEWER_VERBOSITY", "errors") %>">
 <title><%= title %></title>
 
+<%= render "pdfjs_viewer/viewer/before_load", local_assigns %>
+
 <%= stylesheet_link_tag "pdfjs_viewer/application", media: "all" %>
 
 <!-- This snippet is used in production (included from viewer.html) -->