diff --git a/browser/extensions/pdfjs/README.mozilla b/browser/extensions/pdfjs/README.mozilla
index f9123c465736..4ca6510c4357 100644
--- a/browser/extensions/pdfjs/README.mozilla
+++ b/browser/extensions/pdfjs/README.mozilla
@@ -1,5 +1,5 @@
 This is the PDF.js project output, https://github.com/mozilla/pdf.js
 
-Current extension version is: 2.0.602
+Current extension version is: 2.0.625
 
-Taken from upstream commit: 3b07147d
+Taken from upstream commit: e8b50883
diff --git a/browser/extensions/pdfjs/content/build/pdf.js b/browser/extensions/pdfjs/content/build/pdf.js
index d7c6d79d6145..b69b95e9cd7f 100644
--- a/browser/extensions/pdfjs/content/build/pdf.js
+++ b/browser/extensions/pdfjs/content/build/pdf.js
@@ -123,8 +123,8 @@ return /******/ (function(modules) { // webpackBootstrap
 "use strict";
 
 
-var pdfjsVersion = '2.0.602';
-var pdfjsBuild = '3b07147d';
+var pdfjsVersion = '2.0.625';
+var pdfjsBuild = 'e8b50883';
 var pdfjsSharedUtil = __w_pdfjs_require__(1);
 var pdfjsDisplayAPI = __w_pdfjs_require__(6);
 var pdfjsDisplayTextLayer = __w_pdfjs_require__(18);
@@ -825,11 +825,6 @@ var Util = function UtilClosure() {
     var romanStr = romanBuf.join('');
     return lowerCase ? romanStr.toLowerCase() : romanStr;
   };
-  Util.extendObj = function extendObj(obj1, obj2) {
-    for (var key in obj2) {
-      obj1[key] = obj2[key];
-    }
-  };
   Util.inherit = function Util_inherit(sub, base, prototype) {
     sub.prototype = Object.create(base.prototype);
     sub.prototype.constructor = sub;
@@ -4155,10 +4150,10 @@ function getDocument(src) {
     params.disableFontFace = _api_compatibility.apiCompatibilityParams.disableFontFace || false;
   }
   if (typeof params.disableRange !== 'boolean') {
-    params.disableRange = _api_compatibility.apiCompatibilityParams.disableRange || false;
+    params.disableRange = false;
   }
   if (typeof params.disableStream !== 'boolean') {
-    params.disableStream = _api_compatibility.apiCompatibilityParams.disableStream || false;
+    params.disableStream = false;
   }
   if (typeof params.disableAutoFetch !== 'boolean') {
     params.disableAutoFetch = false;
@@ -4228,7 +4223,7 @@ function _fetchDocument(worker, source, pdfDataRangeTransport, docId) {
   }
   return worker.messageHandler.sendWithPromise('GetDocRequest', {
     docId,
-    apiVersion: '2.0.602',
+    apiVersion: '2.0.625',
     source: {
       data: source.data,
       url: source.url,
@@ -4565,7 +4560,7 @@ var PDFPageProxy = function PDFPageProxyClosure() {
               resolve(textContent);
               return;
             }
-            _util.Util.extendObj(textContent.styles, value.styles);
+            Object.assign(textContent.styles, value.styles);
             textContent.items.push(...value.items);
             pump();
           }, reject);
@@ -5362,8 +5357,6 @@ var WorkerTransport = function WorkerTransportClosure() {
     get loadingParams() {
       let params = this._params;
       return (0, _util.shadow)(this, 'loadingParams', {
-        disableRange: params.disableRange,
-        disableStream: params.disableStream,
         disableAutoFetch: params.disableAutoFetch,
         disableCreateObjectURL: params.disableCreateObjectURL,
         disableFontFace: params.disableFontFace,
@@ -5569,8 +5562,8 @@ var InternalRenderTask = function InternalRenderTaskClosure() {
 }();
 var version, build;
 {
-  exports.version = version = '2.0.602';
-  exports.build = build = '3b07147d';
+  exports.version = version = '2.0.625';
+  exports.build = build = 'e8b50883';
 }
 exports.getDocument = getDocument;
 exports.LoopbackPort = LoopbackPort;
@@ -10067,7 +10060,7 @@ var renderTextLayer = function renderTextLayerClosure() {
               capability.resolve();
               return;
             }
-            _util.Util.extendObj(styleCache, value.styles);
+            Object.assign(styleCache, value.styles);
             this._processItems(value.items, styleCache);
             pump();
           }, capability.reject);
diff --git a/browser/extensions/pdfjs/content/build/pdf.worker.js b/browser/extensions/pdfjs/content/build/pdf.worker.js
index 0a333ad89ab9..bad92125c9c2 100644
--- a/browser/extensions/pdfjs/content/build/pdf.worker.js
+++ b/browser/extensions/pdfjs/content/build/pdf.worker.js
@@ -123,8 +123,8 @@ return /******/ (function(modules) { // webpackBootstrap
 "use strict";
 
 
-var pdfjsVersion = '2.0.602';
-var pdfjsBuild = '3b07147d';
+var pdfjsVersion = '2.0.625';
+var pdfjsBuild = 'e8b50883';
 var pdfjsCoreWorker = __w_pdfjs_require__(1);
 exports.WorkerMessageHandler = pdfjsCoreWorker.WorkerMessageHandler;
 
@@ -327,7 +327,7 @@ var WorkerMessageHandler = {
     var cancelXHRs = null;
     var WorkerTasks = [];
     let apiVersion = docParams.apiVersion;
-    let workerVersion = '2.0.602';
+    let workerVersion = '2.0.625';
     if (apiVersion !== workerVersion) {
       throw new Error(`The API version "${apiVersion}" does not match ` + `the Worker version "${workerVersion}".`);
     }
@@ -1364,11 +1364,6 @@ var Util = function UtilClosure() {
     var romanStr = romanBuf.join('');
     return lowerCase ? romanStr.toLowerCase() : romanStr;
   };
-  Util.extendObj = function extendObj(obj1, obj2) {
-    for (var key in obj2) {
-      obj1[key] = obj2[key];
-    }
-  };
   Util.inherit = function Util_inherit(sub, base, prototype) {
     sub.prototype = Object.create(base.prototype);
     sub.prototype.constructor = sub;
@@ -6466,14 +6461,36 @@ var XRef = function XRefClosure() {
       }
       trailerDict.assignXref(this);
       this.trailer = trailerDict;
-      var encrypt = trailerDict.get('Encrypt');
+      let encrypt;
+      try {
+        encrypt = trailerDict.get('Encrypt');
+      } catch (ex) {
+        if (ex instanceof _util.MissingDataException) {
+          throw ex;
+        }
+        (0, _util.warn)(`XRef.parse - Invalid "Encrypt" reference: "${ex}".`);
+      }
       if ((0, _primitives.isDict)(encrypt)) {
         var ids = trailerDict.get('ID');
         var fileId = ids && ids.length ? ids[0] : '';
         encrypt.suppressEncryption = true;
         this.encrypt = new _crypto.CipherTransformFactory(encrypt, fileId, this.pdfManager.password);
       }
-      if (!(this.root = trailerDict.get('Root'))) {
+      let root;
+      try {
+        root = trailerDict.get('Root');
+      } catch (ex) {
+        if (ex instanceof _util.MissingDataException) {
+          throw ex;
+        }
+        (0, _util.warn)(`XRef.parse - Invalid "Root" reference: "${ex}".`);
+      }
+      if ((0, _primitives.isDict)(root) && root.has('Pages')) {
+        this.root = root;
+      } else {
+        if (!recoveryMode) {
+          throw new _util.XRefParseException();
+        }
         throw new _util.FormatError('Invalid root reference');
       }
     },
@@ -6734,7 +6751,7 @@ var XRef = function XRefClosure() {
                 break;
               }
             }
-            startPos += contentLength;
+            startPos = endPos;
           }
           let content = buffer.subarray(position, position + contentLength);
           var xrefTagOffset = skipUntil(content, 0, xrefBytes);
@@ -6755,7 +6772,7 @@ var XRef = function XRefClosure() {
         this.startXRefQueue.push(xrefStms[i]);
         this.readXRef(true);
       }
-      var dict;
+      let trailerDict;
       for (i = 0, ii = trailers.length; i < ii; ++i) {
         stream.pos = trailers[i];
         var parser = new _parser.Parser(new _parser.Lexer(stream), true, this, true);
@@ -6763,16 +6780,29 @@ var XRef = function XRefClosure() {
         if (!(0, _primitives.isCmd)(obj, 'trailer')) {
           continue;
         }
-        dict = parser.getObj();
+        let dict = parser.getObj();
         if (!(0, _primitives.isDict)(dict)) {
           continue;
         }
+        let rootDict;
+        try {
+          rootDict = dict.get('Root');
+        } catch (ex) {
+          if (ex instanceof _util.MissingDataException) {
+            throw ex;
+          }
+          continue;
+        }
+        if (!(0, _primitives.isDict)(rootDict) || !rootDict.has('Pages')) {
+          continue;
+        }
         if (dict.has('ID')) {
           return dict;
         }
+        trailerDict = dict;
       }
-      if (dict) {
-        return dict;
+      if (trailerDict) {
+        return trailerDict;
       }
       throw new _util.InvalidPDFException('Invalid PDF structure');
     },
@@ -8115,7 +8145,7 @@ var Lexer = function LexerClosure() {
       var ch = this.currentChar;
       var eNotation = false;
       var divideBy = 0;
-      var sign = 1;
+      var sign = 0;
       if (ch === 0x2D) {
         sign = -1;
         ch = this.nextChar();
@@ -8123,10 +8153,7 @@ var Lexer = function LexerClosure() {
           ch = this.nextChar();
         }
       } else if (ch === 0x2B) {
-        ch = this.nextChar();
-      }
-      if (ch === 0x2E) {
-        divideBy = 10;
+        sign = 1;
         ch = this.nextChar();
       }
       if (ch === 0x0A || ch === 0x0D) {
@@ -8134,9 +8161,18 @@ var Lexer = function LexerClosure() {
           ch = this.nextChar();
         } while (ch === 0x0A || ch === 0x0D);
       }
+      if (ch === 0x2E) {
+        divideBy = 10;
+        ch = this.nextChar();
+      }
       if (ch < 0x30 || ch > 0x39) {
+        if (divideBy === 10 && sign === 0 && ((0, _util.isSpace)(ch) || ch === -1)) {
+          (0, _util.warn)('Lexer.getNumber - treating a single decimal point as zero.');
+          return 0;
+        }
         throw new _util.FormatError(`Invalid number: ${String.fromCharCode(ch)} (charCode ${ch})`);
       }
+      sign = sign || 1;
       var baseValue = ch - 0x30;
       var powerValue = 0;
       var powerValueSign = 1;
@@ -18802,7 +18838,7 @@ var OperatorList = function OperatorListClosure() {
       }
     },
     addOpList(opList) {
-      _util.Util.extendObj(this.dependencies, opList.dependencies);
+      Object.assign(this.dependencies, opList.dependencies);
       for (var i = 0, ii = opList.length; i < ii; i++) {
         this.addOp(opList.fnArray[i], opList.argsArray[i]);
       }
diff --git a/browser/extensions/pdfjs/content/web/viewer.js b/browser/extensions/pdfjs/content/web/viewer.js
index 5d0028bcd95c..6fb54dce3508 100644
--- a/browser/extensions/pdfjs/content/web/viewer.js
+++ b/browser/extensions/pdfjs/content/web/viewer.js
@@ -3206,10 +3206,6 @@ const defaultOptions = {
     value: './images/',
     kind: OptionKind.VIEWER
   },
-  locale: {
-    value: typeof navigator !== 'undefined' ? navigator.language : 'en-US',
-    kind: OptionKind.VIEWER
-  },
   maxCanvasPixels: {
     value: _viewer_compatibility.viewerCompatibilityParams.maxCanvasPixels || 16777216,
     kind: OptionKind.VIEWER
@@ -3263,11 +3259,11 @@ const defaultOptions = {
     kind: OptionKind.API
   },
   disableRange: {
-    value: _pdfjsLib.apiCompatibilityParams.disableRange || false,
+    value: false,
     kind: OptionKind.API
   },
   disableStream: {
-    value: _pdfjsLib.apiCompatibilityParams.disableStream || false,
+    value: false,
     kind: OptionKind.API
   },
   isEvalSupported: {
@@ -3299,6 +3295,7 @@ const defaultOptions = {
     kind: OptionKind.WORKER
   }
 };
+;
 const userOptions = Object.create(null);
 class AppOptions {
   constructor() {
@@ -6349,7 +6346,7 @@ class PDFViewer extends _base_viewer.BaseViewer {
     return (0, _pdfjsLib.shadow)(this, '_setDocumentViewerElement', this.viewer);
   }
   _scrollIntoView({ pageDiv, pageSpot = null }) {
-    if (!pageSpot) {
+    if (!pageSpot && !this.isInPresentationMode) {
       const left = pageDiv.offsetLeft + pageDiv.clientLeft;
       const right = left + pageDiv.clientWidth;
       const { scrollLeft, clientWidth } = this.container;
@@ -6410,15 +6407,57 @@ class PDFViewer extends _base_viewer.BaseViewer {
       location: this._location
     });
   }
-  _regroupSpreads() {
-    const container = this._setDocumentViewerElement,
-          pages = this._pages;
-    while (container.firstChild) {
-      container.firstChild.remove();
+  get _isScrollModeHorizontal() {
+    return this.isInPresentationMode ? false : this.scrollMode === _base_viewer.ScrollMode.HORIZONTAL;
+  }
+  setScrollMode(mode) {
+    if (mode === this.scrollMode) {
+      return;
     }
+    super.setScrollMode(mode);
+    this.eventBus.dispatch('scrollmodechanged', { mode });
+    this._updateScrollModeClasses();
+    if (!this.pdfDocument) {
+      return;
+    }
+    const pageNumber = this._currentPageNumber;
+    if (isNaN(this._currentScaleValue)) {
+      this._setScale(this._currentScaleValue, true);
+    }
+    this.scrollPageIntoView({ pageNumber });
+    this.update();
+  }
+  _updateScrollModeClasses() {
+    const { scrollMode, viewer } = this;
+    if (scrollMode === _base_viewer.ScrollMode.HORIZONTAL) {
+      viewer.classList.add('scrollHorizontal');
+    } else {
+      viewer.classList.remove('scrollHorizontal');
+    }
+    if (scrollMode === _base_viewer.ScrollMode.WRAPPED) {
+      viewer.classList.add('scrollWrapped');
+    } else {
+      viewer.classList.remove('scrollWrapped');
+    }
+  }
+  setSpreadMode(mode) {
+    if (mode === this.spreadMode) {
+      return;
+    }
+    super.setSpreadMode(mode);
+    this.eventBus.dispatch('spreadmodechanged', { mode });
+    this._regroupSpreads();
+  }
+  _regroupSpreads() {
+    if (!this.pdfDocument) {
+      return;
+    }
+    const viewer = this.viewer,
+          pages = this._pages;
+    viewer.textContent = '';
     if (this.spreadMode === _base_viewer.SpreadMode.NONE) {
       for (let i = 0, iMax = pages.length; i < iMax; ++i) {
-        container.appendChild(pages[i].div);
+        viewer.appendChild(pages[i].div);
       }
     } else {
       const parity = this.spreadMode - 1;
@@ -6427,10 +6466,10 @@ class PDFViewer extends _base_viewer.BaseViewer {
         if (spread === null) {
           spread = document.createElement('div');
           spread.className = 'spread';
-          container.appendChild(spread);
+          viewer.appendChild(spread);
         } else if (i % 2 === parity) {
           spread = spread.cloneNode(false);
-          container.appendChild(spread);
+          viewer.appendChild(spread);
         }
         spread.appendChild(pages[i].div);
       }
@@ -6554,7 +6593,9 @@ class BaseViewer {
     if (this.removePageBorders) {
       this.viewer.classList.add('removePageBorders');
     }
-    this._updateScrollModeClasses();
+    if (this.scrollMode !== ScrollMode.VERTICAL) {
+      this._updateScrollModeClasses();
+    }
   }
   get pagesCount() {
     return this._pages.length;
@@ -6858,9 +6899,10 @@ class BaseViewer {
       if (!currentPage) {
         return;
       }
-      let hPadding = this.isInPresentationMode || this.removePageBorders ? 0 : _ui_utils.SCROLLBAR_PADDING;
-      let vPadding = this.isInPresentationMode || this.removePageBorders ? 0 : _ui_utils.VERTICAL_PADDING;
-      if (this.scrollMode === ScrollMode.HORIZONTAL) {
+      const noPadding = this.isInPresentationMode || this.removePageBorders;
+      let hPadding = noPadding ? 0 : _ui_utils.SCROLLBAR_PADDING;
+      let vPadding = noPadding ? 0 : _ui_utils.VERTICAL_PADDING;
+      if (!noPadding && this._isScrollModeHorizontal) {
         const temp = hPadding;
         hPadding = vPadding;
         vPadding = temp;
@@ -7030,6 +7072,9 @@ class BaseViewer {
   focus() {
     this.container.focus();
   }
+  get _isScrollModeHorizontal() {
+    throw new Error('Not implemented: _isScrollModeHorizontal');
+  }
   get isInPresentationMode() {
     return this.presentationModeState === _ui_utils.PresentationModeState.FULLSCREEN;
   }
@@ -7082,7 +7127,7 @@ class BaseViewer {
   }
   forceRendering(currentlyVisiblePages) {
     let visiblePages = currentlyVisiblePages || this._getVisiblePages();
-    let scrollAhead = this.scrollMode === ScrollMode.HORIZONTAL ? this.scroll.right : this.scroll.down;
+    let scrollAhead = this._isScrollModeHorizontal ? this.scroll.right : this.scroll.down;
     let pageView = this.renderingQueue.getHighestPriority(visiblePages, this._pages, scrollAhead);
     if (pageView) {
       this._ensurePdfPageLoaded(pageView).then(() => {
@@ -7156,30 +7201,17 @@ class BaseViewer {
     });
   }
   setScrollMode(mode) {
-    if (mode !== this.scrollMode) {
-      this.scrollMode = mode;
-      this._updateScrollModeClasses();
-      this.eventBus.dispatch('scrollmodechanged', { mode });
-      const pageNumber = this._currentPageNumber;
-      if (isNaN(this._currentScaleValue)) {
-        this._setScale(this._currentScaleValue, this.isInPresentationMode);
-      }
-      this.scrollPageIntoView({ pageNumber });
-      this.update();
+    if (!Number.isInteger(mode) || !Object.values(ScrollMode).includes(mode)) {
+      throw new Error(`Invalid scroll mode: ${mode}`);
     }
+    this.scrollMode = mode;
   }
-  _updateScrollModeClasses() {
-    const mode = this.scrollMode,
-          { classList } = this.viewer;
-    classList.toggle('scrollHorizontal', mode === ScrollMode.HORIZONTAL);
-    classList.toggle('scrollWrapped', mode === ScrollMode.WRAPPED);
-  }
+  _updateScrollModeClasses() {}
   setSpreadMode(mode) {
-    if (mode !== this.spreadMode) {
-      this.spreadMode = mode;
-      this.eventBus.dispatch('spreadmodechanged', { mode });
-      this._regroupSpreads();
+    if (!Number.isInteger(mode) || !Object.values(SpreadMode).includes(mode)) {
+      throw new Error(`Invalid spread mode: ${mode}`);
     }
+    this.spreadMode = mode;
   }
   _regroupSpreads() {}
 }
@@ -8176,16 +8208,38 @@ class SecondaryToolbar {
   }
   _bindScrollModeListener(buttons) {
     this.eventBus.on('scrollmodechanged', function (evt) {
-      buttons.scrollVerticalButton.classList.toggle('toggled', evt.mode === _base_viewer.ScrollMode.VERTICAL);
-      buttons.scrollHorizontalButton.classList.toggle('toggled', evt.mode === _base_viewer.ScrollMode.HORIZONTAL);
-      buttons.scrollWrappedButton.classList.toggle('toggled', evt.mode === _base_viewer.ScrollMode.WRAPPED);
+      buttons.scrollVerticalButton.classList.remove('toggled');
+      buttons.scrollHorizontalButton.classList.remove('toggled');
+      buttons.scrollWrappedButton.classList.remove('toggled');
+      switch (evt.mode) {
+        case _base_viewer.ScrollMode.VERTICAL:
+          buttons.scrollVerticalButton.classList.add('toggled');
+          break;
+        case _base_viewer.ScrollMode.HORIZONTAL:
+          buttons.scrollHorizontalButton.classList.add('toggled');
+          break;
+        case _base_viewer.ScrollMode.WRAPPED:
+          buttons.scrollWrappedButton.classList.add('toggled');
+          break;
+      }
     });
   }
   _bindSpreadModeListener(buttons) {
     this.eventBus.on('spreadmodechanged', function (evt) {
-      buttons.spreadNoneButton.classList.toggle('toggled', evt.mode === _base_viewer.SpreadMode.NONE);
-      buttons.spreadOddButton.classList.toggle('toggled', evt.mode === _base_viewer.SpreadMode.ODD);
-      buttons.spreadEvenButton.classList.toggle('toggled', evt.mode === _base_viewer.SpreadMode.EVEN);
+      buttons.spreadNoneButton.classList.remove('toggled');
+      buttons.spreadOddButton.classList.remove('toggled');
+      buttons.spreadEvenButton.classList.remove('toggled');
+      switch (evt.mode) {
+        case _base_viewer.SpreadMode.NONE:
+          buttons.spreadNoneButton.classList.add('toggled');
+          break;
+        case _base_viewer.SpreadMode.ODD:
+          buttons.spreadOddButton.classList.add('toggled');
+          break;
+        case _base_viewer.SpreadMode.EVEN:
+          buttons.spreadEvenButton.classList.add('toggled');
+          break;
+      }
     });
   }
   open() {