--- a/browser/components/extensions/ext-tabs.js
+++ b/browser/components/extensions/ext-tabs.js
@@ -877,60 +877,91 @@ this.tabs = class extends ExtensionAPI {
           picker.appendFilter("PDF", "*.pdf");
           picker.defaultExtension = "pdf";
           picker.defaultString = activeTab.linkedBrowser.contentTitle + ".pdf";
 
           return new Promise(resolve => {
             picker.open(function(retval) {
               if (retval == 0 || retval == 2) {
                 // OK clicked (retval == 0) or replace confirmed (retval == 2)
+
+                // Workaround: When trying to replace an existing file that is open in another application (i.e. a locked file),
+                // the print progress listener is never called. This workaround ensures that a correct status is always returned.
                 try {
                   let fstream = Cc["@mozilla.org/network/file-output-stream;1"].createInstance(Ci.nsIFileOutputStream);
-                  fstream.init(picker.file, 0x2A, 0x1B6, 0); // write|create|truncate, file permissions rw-rw-rw- = 0666 = 0x1B6
-                  fstream.close(); // unlock file
+                  fstream.init(picker.file, 0x2A, 0o666, 0); // ioflags = write|create|truncate, file permissions = rw-rw-rw-
+                  fstream.close();
                 } catch (e) {
                   resolve(retval == 0 ? "not_saved" : "not_replaced");
                   return;
                 }
 
                 let psService = Cc["@mozilla.org/gfx/printsettings-service;1"].getService(Ci.nsIPrintSettingsService);
                 let printSettings = psService.newPrintSettings;
 
+                printSettings.printerName = "";
+                printSettings.isInitializedFromPrinter = true;
+                printSettings.isInitializedFromPrefs = true;
+
                 printSettings.printToFile = true;
                 printSettings.toFileName = picker.file.path;
 
                 printSettings.printSilent = true;
                 printSettings.showPrintProgress = false;
 
                 printSettings.printFrameType = Ci.nsIPrintSettings.kFramesAsIs;
                 printSettings.outputFormat = Ci.nsIPrintSettings.kOutputFormatPDF;
 
+                if (pageSettings.paperSizeUnit !== null) {
+                  printSettings.paperSizeUnit = pageSettings.paperSizeUnit;
+                }
+                if (pageSettings.paperWidth !== null) {
+                  printSettings.paperWidth = pageSettings.paperWidth;
+                }
+                if (pageSettings.paperHeight !== null) {
+                  printSettings.paperHeight = pageSettings.paperHeight;
+                }
                 if (pageSettings.orientation !== null) {
                   printSettings.orientation = pageSettings.orientation;
                 }
                 if (pageSettings.scaling !== null) {
                   printSettings.scaling = pageSettings.scaling;
                 }
                 if (pageSettings.shrinkToFit !== null) {
                   printSettings.shrinkToFit = pageSettings.shrinkToFit;
                 }
                 if (pageSettings.showBackgroundColors !== null) {
                   printSettings.printBGColors = pageSettings.showBackgroundColors;
                 }
                 if (pageSettings.showBackgroundImages !== null) {
                   printSettings.printBGImages = pageSettings.showBackgroundImages;
                 }
-                if (pageSettings.paperSizeUnit !== null) {
-                  printSettings.paperSizeUnit = pageSettings.paperSizeUnit;
+                if (pageSettings.edgeLeft !== null) {
+                  printSettings.edgeLeft = pageSettings.edgeLeft;
+                }
+                if (pageSettings.edgeRight !== null) {
+                  printSettings.edgeRight = pageSettings.edgeRight;
+                }
+                if (pageSettings.edgeTop !== null) {
+                  printSettings.edgeTop = pageSettings.edgeTop;
+                }
+                if (pageSettings.edgeBottom !== null) {
+                  printSettings.edgeBottom = pageSettings.edgeBottom;
                 }
-                if (pageSettings.paperWidth !== null) {
-                  printSettings.paperWidth = pageSettings.paperWidth;
+                if (pageSettings.marginLeft !== null) {
+                  printSettings.marginLeft = pageSettings.marginLeft;
+                }
+                if (pageSettings.marginRight !== null) {
+                  printSettings.marginRight = pageSettings.marginRight;
                 }
-                if (pageSettings.paperHeight !== null) {
-                  printSettings.paperHeight = pageSettings.paperHeight;
+                if (pageSettings.marginTop !== null) {
+                  printSettings.marginTop = pageSettings.marginTop;
+                }
+                if (pageSettings.marginBottom !== null) {
+                  printSettings.marginBottom = pageSettings.marginBottom;
                 }
                 if (pageSettings.headerLeft !== null) {
                   printSettings.headerStrLeft = pageSettings.headerLeft;
                 }
                 if (pageSettings.headerCenter !== null) {
                   printSettings.headerStrCenter = pageSettings.headerCenter;
                 }
                 if (pageSettings.headerRight !== null) {
@@ -940,32 +971,35 @@ this.tabs = class extends ExtensionAPI {
                   printSettings.footerStrLeft = pageSettings.footerLeft;
                 }
                 if (pageSettings.footerCenter !== null) {
                   printSettings.footerStrCenter = pageSettings.footerCenter;
                 }
                 if (pageSettings.footerRight !== null) {
                   printSettings.footerStrRight = pageSettings.footerRight;
                 }
-                if (pageSettings.marginLeft !== null) {
-                  printSettings.marginLeft = pageSettings.marginLeft;
-                }
-                if (pageSettings.marginRight !== null) {
-                  printSettings.marginRight = pageSettings.marginRight;
-                }
-                if (pageSettings.marginTop !== null) {
-                  printSettings.marginTop = pageSettings.marginTop;
-                }
-                if (pageSettings.marginBottom !== null) {
-                  printSettings.marginBottom = pageSettings.marginBottom;
-                }
 
-                activeTab.linkedBrowser.print(activeTab.linkedBrowser.outerWindowID, printSettings, null);
+                let printProgressListener = {
+                  onLocationChange(webProgress, request, location, flags) { },
+                  onProgressChange(webProgress, request, curSelfProgress, maxSelfProgress, curTotalProgress, maxTotalProgress) { },
+                  onSecurityChange(webProgress, request, state) { },
+                  onStateChange(webProgress, request, flags, status) {
+                    if ((flags & Ci.nsIWebProgressListener.STATE_STOP) && (flags & Ci.nsIWebProgressListener.STATE_IS_DOCUMENT)) {
+                      resolve(retval == 0 ? "saved" : "replaced");
+                    }
+                  },
+                  onStatusChange: function(webProgress, request, status, message) {
+                    if (status != 0) {
+                      resolve(retval == 0 ? "not_saved" : "not_replaced");
+                    }
+                  },
+                  QueryInterface: XPCOMUtils.generateQI([Ci.nsIWebProgressListener]),
+                };
 
-                resolve(retval == 0 ? "saved" : "replaced");
+                activeTab.linkedBrowser.print(activeTab.linkedBrowser.outerWindowID, printSettings, printProgressListener);
               } else {
                 // Cancel clicked (retval == 1)
                 resolve("canceled");
               }
             });
           });
         },
 

--- a/browser/components/extensions/schemas/tabs.json
+++ b/browser/components/extensions/schemas/tabs.json
@@ -137,16 +137,31 @@
           }
         }
       },
       {
         "id": "PageSettings",
         "type": "object",
         "description": "The page settings including: orientation, scale, background, margins, headers, footers.",
         "properties": {
+          "paperSizeUnit": {
+            "type": "integer",
+            "optional": true,
+            "description": "The page size unit: 0 = inches, 1 = millimeters. Default: 0."
+          },
+          "paperWidth": {
+            "type": "number",
+            "optional": true,
+            "description": "The paper width in paper size units. Default: 8.5."
+          },
+          "paperHeight": {
+            "type": "number",
+            "optional": true,
+            "description": "The paper height in paper size units. Default: 11.0."
+          },
           "orientation": {
             "type": "integer",
             "optional": true,
             "description": "The page content orientation: 0 = portrait, 1 = landscape. Default: 0."
           },
           "scaling": {
             "type": "number",
             "optional": true,
@@ -162,30 +177,55 @@
             "optional": true,
             "description": "Whether the page background colors should be shown. Default: false."
           },
           "showBackgroundImages": {
             "type": "boolean",
             "optional": true,
             "description": "Whether the page background images should be shown. Default: false."
           },
-          "paperSizeUnit": {
-            "type": "integer",
+          "edgeLeft": {
+            "type": "number",
+            "optional": true,
+            "description": "The spacing between the left header/footer and the left edge of the paper (inches). Default: 0."
+          },
+          "edgeRight": {
+            "type": "number",
             "optional": true,
-            "description": "The page size unit: 0 = inches, 1 = millimeters. Default: 0."
+            "description": "The spacing between the right header/footer and the right edge of the paper (inches). Default: 0."
           },
-          "paperWidth": {
+          "edgeTop": {
+            "type": "number",
+            "optional": true,
+            "description": "The spacing between the top of the headers and the top edge of the paper (inches). Default: 0"
+          },
+          "edgeBottom": {
             "type": "number",
             "optional": true,
-            "description": "The paper width in paper size units. Default: 8.5."
+            "description": "The spacing between the bottom of the footers and the bottom edge of the paper (inches). Default: 0."
           },
-          "paperHeight": {
+          "marginLeft": {
+            "type": "number",
+            "optional": true,
+            "description": "The margin between the page content and the left edge of the paper (inches). Default: 0.5."
+          },
+          "marginRight": {
             "type": "number",
             "optional": true,
-            "description": "The paper height in paper size units. Default: 11.0."
+            "description": "The margin between the page content and the right edge of the paper (inches). Default: 0.5."
+          },
+          "marginTop": {
+            "type": "number",
+            "optional": true,
+            "description": "The margin between the page content and the top edge of the paper (inches). Default: 0.5."
+          },
+          "marginBottom": {
+            "type": "number",
+            "optional": true,
+            "description": "The margin between the page content and the bottom edge of the paper (inches). Default: 0.5."
           },
           "headerLeft": {
             "type": "string",
             "optional": true,
             "description": "The text for the page's left header. Default: '&T'."
           },
           "headerCenter": {
             "type": "string",
@@ -206,36 +246,16 @@
             "type": "string",
             "optional": true,
             "description": "The text for the page's center footer. Default: ''."
           },
           "footerRight": {
             "type": "string",
             "optional": true,
             "description": "The text for the page's right footer. Default: '&D'."
-          },
-          "marginLeft": {
-            "type": "number",
-            "optional": true,
-            "description": "The margin between the page content and the left edge of the paper (inches). Default: 0.5."
-          },
-          "marginRight": {
-            "type": "number",
-            "optional": true,
-            "description": "The margin between the page content and the right edge of the paper (inches). Default: 0.5."
-          },
-          "marginTop": {
-            "type": "number",
-            "optional": true,
-            "description": "The margin between the page content and the top edge of the paper (inches). Default: 0.5."
-          },
-          "marginBottom": {
-            "type": "number",
-            "optional": true,
-            "description": "The margin between the page content and the bottom edge of the paper (inches). Default: 0.5."
           }
         }
       },
       {
         "id": "TabStatus",
         "type": "string",
         "enum": ["loading", "complete"],
         "description": "Whether the tabs have completed loading."

--- a/browser/components/extensions/test/browser/browser-common.ini
+++ b/browser/components/extensions/test/browser/browser-common.ini
@@ -164,16 +164,18 @@ skip-if = !e10s
 [browser_ext_tabs_onHighlighted.js]
 [browser_ext_tabs_onUpdated.js]
 [browser_ext_tabs_opener.js]
 [browser_ext_tabs_printPreview.js]
 [browser_ext_tabs_query.js]
 [browser_ext_tabs_readerMode.js]
 [browser_ext_tabs_reload.js]
 [browser_ext_tabs_reload_bypass_cache.js]
+[browser_ext_tabs_saveAsPDF.js]
+skip-if = os == 'mac' # Save as PDF not supported on Mac OS X
 [browser_ext_tabs_sendMessage.js]
 [browser_ext_tabs_cookieStoreId.js]
 [browser_ext_tabs_update.js]
 [browser_ext_tabs_zoom.js]
 [browser_ext_tabs_update_url.js]
 [browser_ext_themes_icons.js]
 [browser_ext_themes_validation.js]
 [browser_ext_url_overrides_newtab.js]

new file mode 100644
--- /dev/null
+++ b/browser/components/extensions/test/browser/browser_ext_tabs_saveAsPDF.js
@@ -0,0 +1,103 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+async function testReturnStatus(expectedStatus) {
+  let tab = await BrowserTestUtils.openNewForegroundTab(gBrowser, "http://example.net/");
+
+  let saveDir = FileUtils.getDir("TmpD", [`testSaveDir-${Math.random()}`], true);
+
+  let saveFile = saveDir.clone();
+  saveFile.append("testSaveFile.pdf");
+  if (saveFile.exists()) {
+    saveFile.remove(false);
+  }
+
+  if (expectedStatus == "replaced") {
+    // Create file that can be replaced
+    saveFile.create(Ci.nsIFile.NORMAL_FILE_TYPE, 0o666);
+  } else if (expectedStatus == "not_saved") {
+    // Create directory with same name as file - so that file cannot be saved
+    saveFile.create(Ci.nsIFile.DIRECTORY_TYPE, 0o666);
+  } else if (expectedStatus == "not_replaced") {
+    // Create file that cannot be replaced
+    saveFile.create(Ci.nsIFile.NORMAL_FILE_TYPE, 0o444);
+  }
+
+  let MockFilePicker = SpecialPowers.MockFilePicker;
+  MockFilePicker.init(window);
+
+  if (expectedStatus == "replaced" || expectedStatus == "not_replaced") {
+    MockFilePicker.returnValue = MockFilePicker.returnReplace;
+  } else if (expectedStatus == "canceled") {
+    MockFilePicker.returnValue = MockFilePicker.returnCancel;
+  } else {
+    MockFilePicker.returnValue = MockFilePicker.returnOK;
+  }
+
+  MockFilePicker.displayDirectory = saveDir;
+  MockFilePicker.showCallback = function(fp) {
+    MockFilePicker.setFiles([saveFile]);
+    MockFilePicker.filterIndex = 0; // *.* - all file extensions
+  };
+
+  let manifest = {
+    "description": expectedStatus,
+  };
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: manifest,
+
+    background: async function() {
+      let pageSettings = {};
+
+      let status = await browser.tabs.saveAsPDF(pageSettings);
+
+      let expected = chrome.runtime.getManifest().description;
+
+      browser.test.assertEq(expected, status, "saveAsPDF " + expected);
+
+      browser.test.notifyPass("tabs.saveAsPDF");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("tabs.saveAsPDF");
+  await extension.unload();
+
+  if (expectedStatus == "saved" || expectedStatus == "replaced") {
+    // Check that first four bytes of saved PDF file are "%PDF"
+    let text = await OS.File.read(saveFile.path, {encoding: "utf-8", bytes: 4});
+    is(text, "%PDF", "Got correct magic number");
+  }
+
+  MockFilePicker.cleanup();
+
+  if (expectedStatus == "not_saved" || expectedStatus == "not_replaced") {
+    saveFile.permissions = 0o666;
+  }
+
+  saveDir.remove(true);
+
+  await BrowserTestUtils.removeTab(tab);
+}
+
+add_task(async function testSaveAsPDF_saved() {
+  await testReturnStatus("saved");
+});
+
+add_task(async function testSaveAsPDF_replaced() {
+  await testReturnStatus("replaced");
+});
+
+add_task(async function testSaveAsPDF_canceled() {
+  await testReturnStatus("canceled");
+});
+
+add_task(async function testSaveAsPDF_not_saved() {
+  await testReturnStatus("not_saved");
+});
+
+add_task(async function testSaveAsPDF_not_replaced() {
+  await testReturnStatus("not_replaced");
+});