Use high dpi display hack for printing too.

web/viewer.js

@@ -2089,12 +2089,18 @@ var PageView = function pageView(container, pdfPage, id, scale,
   this.beforePrint = function pageViewBeforePrint() {
     var pdfPage = this.pdfPage;
     var viewport = pdfPage.getViewport(1);
-
+    // Use the same hack we use for high dpi displays for printing to get better
+    // output until bug 811002 is fixed in FF.
+    var PRINT_OUTPUT_SCALE = 2;
     var canvas = this.canvas = document.createElement('canvas');
-    canvas.width = viewport.width;
+    canvas.width = Math.floor(viewport.width) * PRINT_OUTPUT_SCALE;
-    canvas.height = viewport.height;
+    canvas.height = Math.floor(viewport.height) * PRINT_OUTPUT_SCALE;
-    canvas.style.width = viewport.width + 'pt';
+    canvas.style.width = (PRINT_OUTPUT_SCALE * viewport.width) + 'pt';
-    canvas.style.height = viewport.height + 'pt';
+    canvas.style.height = (PRINT_OUTPUT_SCALE * viewport.height) + 'pt';
+    var cssScale = 'scale(' + (1 / PRINT_OUTPUT_SCALE) + ', ' +
+                              (1 / PRINT_OUTPUT_SCALE) + ')';
+    CustomStyle.setProp('transform' , canvas, cssScale);
+    CustomStyle.setProp('transformOrigin' , canvas, '0% 0%');
 
     var printContainer = document.getElementById('printContainer');
     printContainer.appendChild(canvas);
@@ -2102,6 +2108,13 @@ var PageView = function pageView(container, pdfPage, id, scale,
     var self = this;
     canvas.mozPrintCallback = function(obj) {
       var ctx = obj.context;
+
+      ctx.save();
+      ctx.fillStyle = 'rgb(255, 255, 255)';
+      ctx.fillRect(0, 0, canvas.width, canvas.height);
+      ctx.restore();
+      ctx.scale(PRINT_OUTPUT_SCALE, PRINT_OUTPUT_SCALE);
+
       var renderContext = {
         canvasContext: ctx,
         viewport: viewport