How to Annotate and Edit PDFs in Firefox

The Mozilla Firefox web browser features a built-in PDF viewer that allows users to edit and annotate documents directly without needing third-party software. This article provides a straightforward walkthrough on how to open a PDF in Firefox and use its native tools to highlight text, insert custom text boxes, and add freehand ink drawings, as well as how to save your modified file.

Opening the PDF in Firefox

Before you can annotate your document, you must open it within the browser:

  1. Open the Firefox web browser.
  2. Drag and drop your PDF file directly into an open Firefox tab. Alternatively, press Ctrl + O (Windows/Linux) or Cmd + O (Mac) on your keyboard, locate the PDF file on your computer, and click Open.

Highlighting Text

To emphasize specific parts of the document, use the built-in highlighter tool:

  1. Locate the toolbar in the upper-right corner of the PDF viewer and click the Highlight icon (shaped like a marker tip).
  2. A secondary menu will appear allowing you to choose your preferred highlight color and toggle the option to show or hide all highlights.
  3. Click and drag your cursor over the text you want to highlight.
  4. If you are highlighting non-text elements, you can use the freehand highlighter by simply drawing over the desired area while the tool is active.
  5. To remove a highlight, click on the highlighted area and click the Trash can icon that appears.

Inserting Text Boxes

You can easily fill out forms or add notes by inserting text boxes anywhere on the PDF:

  1. Click the Text icon (represented by the letter T) in the upper-right toolbar.
  2. A small drop-down menu will appear where you can select the text color and adjust the font size.
  3. Click anywhere on the PDF page where you want to place your text. A text box will appear.
  4. Type your desired text into the box.
  5. To move the text box, click and drag its border to a new location. To delete it, select the box and click the Trash can icon.

Adding Freehand Ink Drawings

The drawing tool allows you to sign documents, circle information, or sketch directly onto the page:

  1. Click the Draw icon (shaped like a pen) in the upper-right toolbar.
  2. Use the drop-down menu to select your ink color, adjust the line thickness, and change the opacity of the ink.
  3. Click and hold your left mouse button (or use a stylus on a touchscreen device) to draw freely on the PDF.
  4. Once you release the mouse button, the drawing is treated as a single object. You can click on the drawing to resize it, drag it to a new position, or delete it using the Trash can icon.

Saving Your Changes

Annotations made in Firefox are not saved automatically to the original file. To keep your edits:

  1. Click the Save icon (shaped like a floppy disk or a downward arrow in a tray) located in the upper-right toolbar, right next to the annotation tools.
  2. Choose a destination folder on your computer.
  3. Rename the file if you want to keep the original PDF untouched, and click Save. Your annotations are now permanently embedded in the new PDF file.