Running with viewer

In this document

The full version of PDFNetJS can be used to read or modify a PDF opened in WebViewer. This guide will show you how to set up a basic PDFNetJS project that utilizes WebViewer.

By the end of the guide, we will have a project that adds an image to our PDF document and which displays the changes in WebViewer.


This guide will require the following files:

  1. The WebViewer folder from PDFNetJS full.
  2. An empty HTML document.
  3. An empty JavaScript document.
  4. A PDF document of your choice. For this guide we will be using the newsletter PDF document.
  5. An image to add to the PDF document. For this guide we will be using an image of a butterfly.

Setting up the HTML file

Open up index.html with a text editor and copy/paste the following code into the HTML document.

<!DOCTYPE html>
<html style="height:100%;">
    <meta http-equiv="Content-Type" content="text/html">
    <script src="WebViewer/jquery-3.2.1.min.js"></script>
    <script src="WebViewer/lib/WebViewer.min.js"></script>
    <script type="text/javascript">
      $(function() {
        var viewerElement = document.getElementById('viewer');
        var myWebViewer = new PDFTron.WebViewer({
          type: "html5",
          path: "WebViewer/lib",
          initialDoc: "mydoc.pdf",
          config: 'config.js',
          showLocalFilePicker: true,
          pdfnet: true
        }, viewerElement);
  <body style="width:100%;height:100%;margin:0px;padding:0px;overflow:hidden">
    <div id="viewer" style="height: 100%; overflow: hidden;"></div>

Here we include the required jQuery and WebViewer files and start out with a single "viewer" div that we will add content to using a script. In our custom script, new PDFTron.WebViewer is called to create a new WebViewer instance that will be added as a child to our "viewer" div.

Overview of WebViewer initialization parameters:

  • type - Set to "html5".
  • path - String representing the url that points to the WebViewer libraries.
  • initialDoc - String representing the url of the document that will be loaded in WebViewer.
  • config - String that represents the url of the custom script to run once WebViewer finishes loading.
  • showLocalFilePicker - Boolean that determines whether we can open local documents in the viewer.
  • pdfnet - If true, allows PDFNetJS functions to be used.

If you open index.html from a server, you should be able to see your document displayed in WebViewer.

Setting up your JavaScript document

Now that we have our pdf displayed, it's time to write a custom script in config.js. Open up config.js with a text editor and copy/paste the following code into the JavaScript document.

(function() {
  $(document).on('documentLoaded', function() {
      var doc = readerControl.docViewer.getDocument();
        // Ensure that we have our first page.
          // Run our script
            // Refresh the cache with the newly updated document
            // Update viewer with new document

  var runCustomViewerCode = function(doc) {
    function* main() {
      alert("Hello WebViewer!");
    return PDFNet.runGeneratorWithCleanup(main());
//# sourceURL=config.js
In order to run this on browsers without ES6 support, you can convert the file to ES5 using ES6-to-ES5 transformers such as Facebook's regenerator.

If you run the project again in a server, you should be able to see "Hello WebViewer" pop up in an alert box once WebViewer has loaded. Before the custom code is run however, several checks and initializations need to be done first.

  • PDFNet.initialize() - Initializes PDFNetJS backend. This should be called before any PDFNetJS functions are called.
  • doc.getPDFDoc() - Extracts the PDFNet PDFDoc object from the WebViewer document.
  • pdfDoc.requirePage() - Ensures that a particular page of the pdf document is finished downloading before we read or write from it.

    • If the page(s) to be edited cannot be known until the custom script runs, requirePage() can be called instead in the middle of the custom code, but only by unlocking and relocking all operations.
    • An example of this can be seen in the html file of the Viewer Edit test on the samples page.

Writing your custom code

Let us change our main() code to do something more interesting:

function* main() {
  // In WebViewer programs, file searching starts from the WebViewer/lib/html5 folder
  var input_url = "../../../";
  var firstPage =  yield doc.getPage(1);
  // create a new page builder that allows us to create new page elements
  var builder = yield PDFNet.ElementBuilder.create();
  // create a new page writer that allows us to add/change page elements
  var writer = yield PDFNet.ElementWriter.create();
  writer.beginOnPage(firstPage, PDFNet.ElementWriter.WriteMode.e_overlay);

  // Adding a JPEG image to output file
  var img = yield PDFNet.Image.createFromURL(doc, input_url + "butterfly.png");

  var imgWidth = yield img.getImageWidth();
  var imgHeight = yield img.getImageHeight();
  var element = yield builder.createImageScaled(img, 100, 600, imgWidth, imgHeight);

This code sample adds the "butterfly.png" image to location (x:100, y:600) relative to the lower left corner of the document's first page.

Once our custom code has finished running, two final functions readerControl.docViewer.refreshAll() and readerControl.docViewer.updateView() are called to refresh and update the WebViewer display.

The resulting viewer should look like this: