diff --git a/src/display/api.js b/src/display/api.js
index e7035abfe..8c5d231f7 100644
--- a/src/display/api.js
+++ b/src/display/api.js
@@ -383,8 +383,8 @@ var PDFDocumentProxy = (function PDFDocumentProxyClosure() {
  *
  * @typedef {Object} RenderParameters
  * @property {Object} canvasContext - A 2D context of a DOM Canvas object.
- * @property {PageViewport} viewport - Rendering viewport obtained by
- *                          calling of PDFPage.getViewport method.
+ * @property {PDFJS.PageViewport} viewport - Rendering viewport obtained by
+ *                                calling of PDFPage.getViewport method.
  * @property {string} intent - Rendering intent, can be 'display' or 'print'
  *                    (default value is 'display').
  * @property {Object} imageLayer - (optional) An object that has beginLayout,
@@ -442,8 +442,8 @@ var PDFPageProxy = (function PDFPageProxyClosure() {
      * @param {number} scale The desired scale of the viewport.
      * @param {number} rotate Degrees to rotate the viewport. If omitted this
      * defaults to the page rotation.
-     * @return {PageViewport} Contains 'width' and 'height' properties along
-     * with transforms required for rendering.
+     * @return {PDFJS.PageViewport} Contains 'width' and 'height' properties
+     * along with transforms required for rendering.
      */
     getViewport: function PDFPageProxy_getViewport(scale, rotate) {
       if (arguments.length < 2) {
diff --git a/src/shared/util.js b/src/shared/util.js
index dc7b00a1e..2c1567538 100644
--- a/src/shared/util.js
+++ b/src/shared/util.js
@@ -734,7 +734,22 @@ var Util = PDFJS.Util = (function UtilClosure() {
   return Util;
 })();
 
+/**
+ * PDF page viewport created based on scale, rotation and offset.
+ * @class
+ * @alias PDFJS.PageViewport
+ */
 var PageViewport = PDFJS.PageViewport = (function PageViewportClosure() {
+  /**
+   * @constructor
+   * @private
+   * @param viewBox {Array} xMin, yMin, xMax and yMax coordinates.
+   * @param scale {number} scale of the viewport.
+   * @param rotation {number} rotations of the viewport in degrees.
+   * @param offsetX {number} offset X
+   * @param offsetY {number} offset Y
+   * @param dontFlip {boolean} if true, axis Y will not be flipped.
+   */
   function PageViewport(viewBox, scale, rotation, offsetX, offsetY, dontFlip) {
     this.viewBox = viewBox;
     this.scale = scale;
@@ -798,7 +813,14 @@ var PageViewport = PDFJS.PageViewport = (function PageViewportClosure() {
     this.height = height;
     this.fontScale = scale;
   }
-  PageViewport.prototype = {
+  PageViewport.prototype = /** @lends PDFJS.PageViewport.prototype */ {
+    /**
+     * Clones viewport with additional properties.
+     * @param args {Object} (optional) If specified, may contain the 'scale' or
+     * 'rotation' properties to override the corresponding properties in
+     * the cloned viewport.
+     * @returns {PDFJS.PageViewport} Cloned viewport.
+     */
     clone: function PageViewPort_clone(args) {
       args = args || {};
       var scale = 'scale' in args ? args.scale : this.scale;
@@ -806,15 +828,41 @@ var PageViewport = PDFJS.PageViewport = (function PageViewportClosure() {
       return new PageViewport(this.viewBox.slice(), scale, rotation,
                               this.offsetX, this.offsetY, args.dontFlip);
     },
+    /**
+     * Converts PDF point to the viewport coordinates. For examples, useful for
+     * converting PDF location into canvas pixel coordinates.
+     * @param x {number} X coordinate.
+     * @param y {number} Y coordinate.
+     * @returns {Object} Object that contains 'x' and 'y' properties of the
+     * point in the viewport coordinate space.
+     * @see {@link convertToPdfPoint}
+     * @see {@link convertToViewportRectangle}
+     */
     convertToViewportPoint: function PageViewport_convertToViewportPoint(x, y) {
       return Util.applyTransform([x, y], this.transform);
     },
+    /**
+     * Converts PDF rectangle to the viewport coordinates.
+     * @param rect {Array} xMin, yMin, xMax and yMax coordinates.
+     * @returns {Array} Contains corresponding coordinates of the rectangle
+     * in the viewport coordinate space.
+     * @see {@link convertToViewportPoint}
+     */
     convertToViewportRectangle:
       function PageViewport_convertToViewportRectangle(rect) {
       var tl = Util.applyTransform([rect[0], rect[1]], this.transform);
       var br = Util.applyTransform([rect[2], rect[3]], this.transform);
       return [tl[0], tl[1], br[0], br[1]];
     },
+    /**
+     * Converts viewport coordinates to the PDF location. For examples, useful
+     * for converting canvas pixel location into PDF one.
+     * @param x {number} X coordinate.
+     * @param y {number} Y coordinate.
+     * @returns {Object} Object that contains 'x' and 'y' properties of the
+     * point in the PDF coordinate space.
+     * @see {@link convertToViewportPoint}
+     */
     convertToPdfPoint: function PageViewport_convertToPdfPoint(x, y) {
       return Util.applyInverseTransform([x, y], this.transform);
     }
@@ -944,6 +992,8 @@ function isPDFFunction(v) {
 
 /**
  * Creates a promise capability object.
+ * @alias PDFJS.createPromiseCapability
+ *
  * @return {PromiseCapability} A capability object contains:
  * - a Promise, resolve and reject methods.
  */