diff --git a/UPDATE.md b/UPDATE.md
index 81652947..a3f44823 100644
--- a/UPDATE.md
+++ b/UPDATE.md
@@ -58,10 +58,12 @@ PDFJS.cMapUrl = '../web/cmaps/';
 with
 ``` javascript
 PDFJS.imageResourcesPath = '/pdfjs/web/images/';
-PDFJS.workerSrc = '/pdfjs/web/pdf.worker.js';
+PDFJS.workerSrc = '/pdfjs/web/pdf.worker.js?version=<version_number>';
 PDFJS.cMapUrl = '/pdfjs/web/cmaps/';
 ```
 
+The version is added as a query string above so we ensure users will get the matching version of the worker despite caching.
+
 ## `app/assets/stylesheets/pdfjs_viewer/pdfjs/viewer.css`
 
 Replace all `url(images/` with `url(/pdfjs/web/images/`
diff --git a/app/assets/javascripts/pdfjs_viewer/viewer.js b/app/assets/javascripts/pdfjs_viewer/viewer.js
index e8f8b37e..f53c073f 100644
--- a/app/assets/javascripts/pdfjs_viewer/viewer.js
+++ b/app/assets/javascripts/pdfjs_viewer/viewer.js
@@ -941,7 +941,7 @@ var DEFAULT_SCALE_DELTA = 1.1;
 var DISABLE_AUTO_FETCH_LOADING_BAR_TIMEOUT = 5000;
 function configure(PDFJS) {
   PDFJS.imageResourcesPath = '/pdfjs/web/images/';
-  PDFJS.workerSrc = '/pdfjs/web/pdf.worker.js';
+  PDFJS.workerSrc = '/pdfjs/web/pdf.worker.js?version=1.10.100';
   PDFJS.cMapUrl = '/pdfjs/web/cmaps/';
   PDFJS.cMapPacked = true;
 }