title: PDF.js render pdf with scrollbar
body: <p>I use mozilla pdf.js. I have a code:</p>
  
  <pre><code>&lt;canvas id="the-canvas"/&gt;
  function displayDocument(){
          PDFJS.getDocument(numberOdDocument[attachment]).then(function (pdfDoc_) {
              pdfDoc = pdfDoc_;
              renderPage(pageNum);
            });
      }
  function renderPage(num) {
          pdfDoc.getPage(num).then(function(page) {
            var viewport = page.getViewport(scale, rotate);
            canvas.height = '900';
            canvas.width = '500';
  
            var renderContext = {
              canvasContext: ctx,
              viewport: viewport
            };
            var renderTask = page.render(renderContext);
  
            renderTask.promise.then(function () {
              pageRendering = false;
              if (pageNumPending !== null) {
                renderPage(pageNumPending);
                pageNumPending = null;
              }
            });
          });
      }
  </code></pre>
  
  <p>Now i see only one page in canvas tag, but I want add scrollbar to my canvvas, and I want change page with scroll. How can I do that?</p>