Tech

How to Annotate PDFs in Mozilla Firefox


Mozilla Firefox, like Edge and Chrome, is a browser with which you can open and view PDF documents. However, unlike Edge, Firefox’s PDF toolbar doesn’t include any annotation options by default.

Despite this, you still have options to annotate PDF files in Firefox with and without additional browser add-ons. Here, we’ll take a look at how.


How to Annotate PDFs With Firefox’s PDF Viewer

Ok, Firefox’s PDF viewer doesn’t appear to have any annotation options. However, you can enable new editing tools for PDF files in that browser by changing a hidden advanced preference.

Then you can select new text and drawing options for PDFs in Firefox. This is how to enable and utilize Fox’s PDF annotation tools:

  1. To open the Advanced Preferences page tab, input about:config in Fox’s URL address bar and press Return.
  2. Press the Accept the Risk button (there isn’t any risk for enabling PDF tools).

  3. Then input pdfjs.annotationEditorMode in the search preference text box.
  4. Double-click the pdfjs.annotationEditorMode preference to activate its text box.
  5. Input a 0 value for pdfjs.annotationEditorMode within that setting’s text box, and click the blue Save button.

  6. Next, type pdfjs.annotationMode in the search box.
  7. The pdfjs.annotationMode preference’s value needs to be set at 2. If pdfjs.annotationMode is not set at that value, double-click that preference to input 2 and click Save.

  8. Close Firefox after modifying those about:config settings.
  9. Right-click a PDF file in Explorer to select Open with.

  10. Choose to open a PDF file in Firefox to view it in that browser. Now you should see new Add FreeText Annotation and Add Ink Annotation buttons on the Firefox PDF viewer’s toolbar.


Press the Add FreeText button to bring up text size and color options. Click the Color box to choose a color for the text, and drag the Size bar’s slider to adjust the scale. Then click anywhere inside the PDF to add some text to it.

If you want to scribble on your PDF, click the Add Ink Annotation button. Choose an ink color by clocking the Color box palette. Drag the Thickness bar’s slider left or right to adjust the pen’s width.

You can also change the ink’s transparency level by dragging the slider on the Opacity bar. Left-click anywhere inside the PDF and hold the mouse button to draw on the document.

To save an edited file, click the Download button. Choose a folder to include the PDF in, and input a title in the File name box. Click Save to add the PDF to the selected folder.

How to Annotate PDFs in Firefox With PDF2Go

Firefox’s PDF viewer only has two editing options. If you want to add highlights and shapes to documents, you’ll need to utilize the PDF2Go add-on. PDF2Go is a PDF extension for Firefox that makes editing, compression, conversion, and merging tools for PDF documents accessible within Fox.

To install that extension, open the PDF2Go page linked below in Firefox. Select PDF2Go’s Add to Firefox option, and click Add again for confirmation. Then you’ll see an Online PDF Editor button on Fox’s URL toolbar.

Click the Online PDF Editor button to bring up its menu. Select Edit PDF to open a page with a Choose File option. Press the Choose File button, select a PDF, and click Open.

Now you can get started editing your PDF. Press the Highlight button on the toolbar. Then hold the mouse’s left button and drag a yellow box over the text you need to highlight in the open document.


If you want to add shapes, click the Arrow, Rectangle, or Ellipse options. Then drag the shapes onto the document by holding the left mouse button and moving the cursor.

You can add notes by clicking the Text button. Click a position in the document to place the text box, and then drag its corners with the cursor to resize. Then you can input text within the box. Press the Options button to access settings for changing the color, size, and style of your text box’s font.

When you’ve finished, click the Save as button. Select Save to convert the file. Press Download to save it to a local folder.

Download: PDF2Go – PDF Editor & Converter (Free)

Annotate Your PDF Documents in Firefox Instead of Edge

So, Firefox users don’t need to switch to Edge for annotating PDF files. Enabling Firefox’s built-in PDF editing options and adding the PDF2Go extension to that browser will give you most of the PDF annotation tools you’ll probably need. You can add text, scribbles, shapes, and highlights to your PDF files with those tools.

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