diff --git a/browser/components/extensions/parent/ext-tabs.js b/browser/components/extensions/parent/ext-tabs.js
index c14df61416eee..b455b0d9d0459 100644
--- a/browser/components/extensions/parent/ext-tabs.js
+++ b/browser/components/extensions/parent/ext-tabs.js
@@ -1292,11 +1292,6 @@ this.tabs = class extends ExtensionAPI {
           let title = strBundle.GetStringFromName(
             "saveaspdf.saveasdialog.title"
           );
-
-          if (AppConstants.platform === "macosx") {
-            return Promise.reject({ message: "Not supported on Mac OS X" });
-          }
-
           let filename;
           if (
             pageSettings.toFileName !== null &&
diff --git a/browser/components/extensions/test/browser/browser.ini b/browser/components/extensions/test/browser/browser.ini
index 7e0a42be26294..a0bb887e7acd3 100644
--- a/browser/components/extensions/test/browser/browser.ini
+++ b/browser/components/extensions/test/browser/browser.ini
@@ -264,7 +264,6 @@ skip-if = !e10s
 [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_sharingState.js]
 [browser_ext_tabs_successors.js]
diff --git a/widget/cocoa/nsPrintSettingsServiceX.mm b/widget/cocoa/nsPrintSettingsServiceX.mm
index cbaa959e98a04..59d6b350c6e4b 100644
--- a/widget/cocoa/nsPrintSettingsServiceX.mm
+++ b/widget/cocoa/nsPrintSettingsServiceX.mm
@@ -65,7 +65,11 @@
 
   NSURL* printToFileURL = [dict objectForKey:NSPrintJobSavingURL];
   if (printToFileURL) {
-    nsCocoaUtils::GetStringForNSString([printToFileURL absoluteString], data -> toFileName());
+    if ([printToFileURL isFileURL]) {
+      nsCocoaUtils::GetStringForNSString([printToFileURL path], data->toFileName());
+    } else {
+      MOZ_ASSERT_UNREACHABLE("expected a file URL");
+    }
   }
 
   NSDate* printTime = [dict objectForKey:NSPrintTime];
diff --git a/widget/cocoa/nsPrintSettingsX.mm b/widget/cocoa/nsPrintSettingsX.mm
index 8323339e86600..60c5c6777fefc 100644
--- a/widget/cocoa/nsPrintSettingsX.mm
+++ b/widget/cocoa/nsPrintSettingsX.mm
@@ -235,8 +235,16 @@
 
 NS_IMETHODIMP
 nsPrintSettingsX::GetEffectivePageSize(double* aWidth, double* aHeight) {
-  *aWidth = NS_INCHES_TO_TWIPS(mAdjustedPaperWidth / mWidthScale);
-  *aHeight = NS_INCHES_TO_TWIPS(mAdjustedPaperHeight / mHeightScale);
+  if (kPaperSizeInches == GetCocoaUnit(mPaperSizeUnit)) {
+    *aWidth = NS_INCHES_TO_TWIPS(mAdjustedPaperWidth / mWidthScale);
+    *aHeight = NS_INCHES_TO_TWIPS(mAdjustedPaperHeight / mHeightScale);
+  } else {
+    *aWidth = NS_MILLIMETERS_TO_TWIPS(mAdjustedPaperWidth / mWidthScale);
+    *aHeight = NS_MILLIMETERS_TO_TWIPS(mAdjustedPaperHeight / mHeightScale);
+  }
+  if (kLandscapeOrientation == mOrientation) {
+    std::swap(*aWidth, *aHeight);
+  }
   return NS_OK;
 }