--- a/browser/components/nsBrowserGlue.js
+++ b/browser/components/nsBrowserGlue.js
@@ -508,17 +508,16 @@ BrowserGlue.prototype = {
     DirectoryLinksProvider.init();
     NewTabUtils.links.addProvider(DirectoryLinksProvider);
     BrowserNewTabPreloader.init();
 #ifdef NIGHTLY_BUILD
     if (Services.prefs.getBoolPref("dom.identity.enabled")) {
       SignInToWebsiteUX.init();
     }
 #endif
-    PdfJs.init();
 #ifdef NIGHTLY_BUILD
     ShumwayUtils.init();
 #endif
     webrtcUI.init();
     AboutHome.init();
     SessionStore.init();
     BrowserUITelemetry.init();
     ContentSearch.init();
@@ -666,16 +665,29 @@ BrowserGlue.prototype = {
     if (SCALING_PROBE_NAME) {
       let scaling = aWindow.devicePixelRatio * 100;
       Services.telemetry.getHistogramById(SCALING_PROBE_NAME).add(scaling);
     }
   },
 
   // the first browser window has finished initializing
   _onFirstWindowLoaded: function BG__onFirstWindowLoaded(aWindow) {
+    // Initialize PdfJs when running in-process and remote. This only
+    // happens once since PdfJs registers global hooks. If the PdfJs
+    // extension is installed the init method below will be overridden
+    // leaving initialization to the extension.
+    // parent only: configure default prefs, set up pref observers, register
+    // pdf content handler, and initializes parent side message manager
+    // shim for privileged api access.
+    PdfJs.init(true);
+    // child only: similar to the call above for parent - register content
+    // handler and init message manager child shim for privileged api access.
+    // With older versions of the extension installed, this load will fail
+    // passively.
+    aWindow.messageManager.loadFrameScript("resource://pdf.js/pdfjschildbootstrap.js", true);
 #ifdef XP_WIN
     // For windows seven, initialize the jump list module.
     const WINTASKBAR_CONTRACTID = "@mozilla.org/windows-taskbar;1";
     if (WINTASKBAR_CONTRACTID in Cc &&
         Cc[WINTASKBAR_CONTRACTID].getService(Ci.nsIWinTaskbar).available) {
       let temp = {};
       Cu.import("resource:///modules/WindowsJumpLists.jsm", temp);
       temp.WinTaskbarJumpList.startup();