How to display whole PDF (not only one page) with PDF.JS?

Here's my take. Renders all pages in correct order and still works asynchronously.

<style>
  #pdf-viewer {
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.1);
    overflow: auto;
  }
  
  .pdf-page-canvas {
    display: block;
    margin: 5px auto;
    border: 1px solid rgba(0, 0, 0, 0.2);
  }
</style>

<script>   
    url = 'https://github.com/mozilla/pdf.js/blob/master/test/pdfs/tracemonkey.pdf';
    var thePdf = null;
    var scale = 1;
    
    PDFJS.getDocument(url).promise.then(function(pdf) {
        thePdf = pdf;
        viewer = document.getElementById('pdf-viewer');
        
        for(page = 1; page <= pdf.numPages; page++) {
          canvas = document.createElement("canvas");    
          canvas.className = 'pdf-page-canvas';         
          viewer.appendChild(canvas);            
          renderPage(page, canvas);
        }
    });
    
    function renderPage(pageNumber, canvas) {
        thePdf.getPage(pageNumber).then(function(page) {
          viewport = page.getViewport({ scale: scale });
          canvas.height = viewport.height;
          canvas.width = viewport.width;          
          page.render({canvasContext: canvas.getContext('2d'), viewport: viewport});
    });
    }
</script>

<div id='pdf-viewer'></div>

The pdfjs-dist library contains parts for building PDF viewer. You can use PDFPageView to render all pages. Based on https://github.com/mozilla/pdf.js/blob/master/examples/components/pageviewer.html :

var url = "https://cdn.mozilla.net/pdfjs/tracemonkey.pdf";
var container = document.getElementById('container');
// Load document
PDFJS.getDocument(url).then(function (doc) {
  var promise = Promise.resolve();
  for (var i = 0; i < doc.numPages; i++) {
    // One-by-one load pages
    promise = promise.then(function (id) {
      return doc.getPage(id + 1).then(function (pdfPage) {
// Add div with page view.
var SCALE = 1.0; 
var pdfPageView = new PDFJS.PDFPageView({
      container: container,
      id: id,
      scale: SCALE,
      defaultViewport: pdfPage.getViewport(SCALE),
      // We can enable text/annotations layers, if needed
      textLayerFactory: new PDFJS.DefaultTextLayerFactory(),
      annotationLayerFactory: new PDFJS.DefaultAnnotationLayerFactory()
    });
    // Associates the actual page with the view, and drawing it
    pdfPageView.setPdfPage(pdfPage);
    return pdfPageView.draw();        
      });
    }.bind(null, i));
  }
  return promise;
});
#container > *:not(:first-child) {
  border-top: solid 1px black; 
}
<link href="https://npmcdn.com/pdfjs-dist/web/pdf_viewer.css" rel="stylesheet"/>
<script src="https://npmcdn.com/pdfjs-dist/web/compatibility.js"></script>
<script src="https://npmcdn.com/pdfjs-dist/build/pdf.js"></script>
<script src="https://npmcdn.com/pdfjs-dist/web/pdf_viewer.js"></script>

<div id="container" class="pdfViewer singlePageView"></div>

The accepted answer is not working anymore (in 2021), due to the API change for var viewport = page.getViewport( 1 ); to var viewport = page.getViewport({scale: scale});, you can try the full working html as below, just copy the content below to a html file, and open it:

<html>
<head>
<script src="https://mozilla.github.io/pdf.js/build/pdf.js"></script>
<head>
<body>
</body>

<script>

var url = 'https://raw.githubusercontent.com/mozilla/pdf.js/ba2edeae/web/compressed.tracemonkey-pldi-09.pdf';

// Loaded via <script> tag, create shortcut to access PDF.js exports.
var pdfjsLib = window['pdfjs-dist/build/pdf'];

// The workerSrc property shall be specified.
pdfjsLib.GlobalWorkerOptions.workerSrc = 'https://mozilla.github.io/pdf.js/build/pdf.worker.js';

var currPage = 1; //Pages are 1-based not 0-based
var numPages = 0;
var thePDF = null;

//This is where you start
pdfjsLib.getDocument(url).promise.then(function(pdf) {

        //Set PDFJS global object (so we can easily access in our page functions
        thePDF = pdf;

        //How many pages it has
        numPages = pdf.numPages;

        //Start with first page
        pdf.getPage( 1 ).then( handlePages );
});


function handlePages(page)
{
    //This gives us the page's dimensions at full scale
    var viewport = page.getViewport( {scale: 1.5} );

    //We'll create a canvas for each page to draw it on
    var canvas = document.createElement( "canvas" );
    canvas.style.display = "block";
    var context = canvas.getContext('2d');

    canvas.height = viewport.height;
    canvas.width = viewport.width;

    //Draw it on the canvas
    page.render({canvasContext: context, viewport: viewport});

    //Add it to the web page
    document.body.appendChild( canvas );

    var line = document.createElement("hr");
    document.body.appendChild( line );

    //Move to next page
    currPage++;
    if ( thePDF !== null && currPage <= numPages )
    {
        thePDF.getPage( currPage ).then( handlePages );
    }
}
</script>

</html>

PDFJS has a member variable numPages, so you'd just iterate through them. BUT it's important to remember that getting a page in pdf.js is asynchronous, so the order wouldn't be guaranteed. So you'd need to chain them. You could do something along these lines:

var currPage = 1; //Pages are 1-based not 0-based
var numPages = 0;
var thePDF = null;

//This is where you start
PDFJS.getDocument(url).then(function(pdf) {

        //Set PDFJS global object (so we can easily access in our page functions
        thePDF = pdf;

        //How many pages it has
        numPages = pdf.numPages;

        //Start with first page
        pdf.getPage( 1 ).then( handlePages );
});



function handlePages(page)
{
    //This gives us the page's dimensions at full scale
    var viewport = page.getViewport( 1 );

    //We'll create a canvas for each page to draw it on
    var canvas = document.createElement( "canvas" );
    canvas.style.display = "block";
    var context = canvas.getContext('2d');
    canvas.height = viewport.height;
    canvas.width = viewport.width;

    //Draw it on the canvas
    page.render({canvasContext: context, viewport: viewport});

    //Add it to the web page
    document.body.appendChild( canvas );

    //Move to next page
    currPage++;
    if ( thePDF !== null && currPage <= numPages )
    {
        thePDF.getPage( currPage ).then( handlePages );
    }
}