Table of Contents

• 1 Use Firefox’s built-in PDF Viewer
  • 1.1 Fill out forms in PDF Viewer
  • 1.2 PDF Viewer toolbar functions
  • 1.3 Edit PDF files
  • 1.4 Highlight in PDF files
    • 1.4.1 Add a highlight
    • 1.4.2 Show/hide all highlights
    • 1.4.3 Edit or delete a highlight
  • 1.5 Comment in PDF files
    • 1.5.1 Create a comment
    • 1.5.2 Edit a comment
    • 1.5.3 Delete a comment
    • 1.5.4 Useful tips
  • 1.6 Add an image to PDF files
    • 1.6.1 Insert an image
    • 1.6.2 Reposition and resize the image
    • 1.6.3 Add Alt Text for accessibility
  • 1.7 Add a signature to a PDF
  • 1.8 Merge PDF files
    • 1.8.1 Merge a PDF into an open document
  • 1.9 Organize and split PDF files
• 2 PDF Viewer keyboard shortcuts
• 3 Troubleshoot problems with the PDF viewer
• 4 Related articles

Highlight in PDF files

Add a highlight

1. To highlight text or an area in a PDF document, first select the desired text or area. Then, click 👁 Firefox PDF highlighting option
   .

   👁 Firefox PDF select text to highlight
   

2. Choose your preferred highlight color, and adjust the thickness of the highlight.

   👁 Firefox PDF highlighting settings
   

Show/hide all highlights

1. To manage the visibility of all highlights in a PDF file, first click the Highlight 👁 Firefox PDF highlighting option
   button at the top right of the PDF page.
2. Then, use the toggle located next to the Show all option to either display or hide all the highlights in the PDF file.

   👁 Show/hide all PDF highlights
   

Edit or delete a highlight

1. Click the area you previously highlighted.

   👁 Edit or delete Firefox PDF highlight
   

2. To change the color of your highlight, click 👁 Color selection dropdown for PDF highlight
   and select a new color.
3. To remove the highlight, click 👁 Trash can icon
   .

Comment in PDF files

Create a comment

1. To add a comment in a PDF document, first select the desired text or area. Next, click 👁 pdfcommenticon
   .

   👁 commentinpdf
   

2. Type your comment, then click Add to save it in the PDF.

Edit a comment

1. Click 👁 pdfcommenticon
   to open comment editing, either:
   • In the PDF, to open a single comment

     👁 inthepdf
     

   • Or from the top right menu to see all comments in the sidebar and click to open one.

     👁 inthesidebar
     

2. Click the Edit comment button.

   👁 editcomment
   

3. Type your changes, then click the Update button

Delete a comment

1. Click 👁 pdfcommenticon
   to open comment editing, then click the Remove comment button.

   👁 removecomment
   

Useful tips

1. You can drag and drop the comment to a new location.

   👁 draganddrop
   

2. To see and manage all comments in a PDF, open the comment sidebar. In the upper right menu, click 👁 pdfcommenticon
   .

   👁 sidebarcomments
   

Add an image to PDF files

In many PDF-related tasks, incorporating images can provide supplementary information to your content.

Insert an image

1. On the top right of the PDF page, click the Add or edit images 👁 Add image to PDF 2
   button.
2. Click + Add image. This will prompt the file selection window.
3. Browse and select the desired image file to add it to the PDF.

Reposition and resize the image

1. Drag and drop the image to your preferred location within the PDF.
2. To adjust the image size, click and drag its borders until it fits your desired dimensions.

Add Alt Text for accessibility

1. After adding the image, click the + Alt text button.
2. In the provided space, either:
   • Write a concise description of the image for screen readers, or
   • Mark the image as decorative if it’s only for visual appeal.
3. Click the Save button to insert the alt text.

   👁 Add image to PDF
   

See Add alt text to images in your PDFs using Firefox to learn everything about Alt Text.

Add a signature to a PDF

Firefox allows you to add your signature to a PDF document.

1. Open the desired PDF in Firefox.
2. In the top right corner of the page, click the Add signature 👁 IG add signature
   button and then click + Add New Signature.

   👁 Add signature
   

3. Choose between Type, Draw or Image, and click the Add button to insert the signature to the document. To re-do the signature before adding, you can select the Clear signature 👁 IG trash
   option.

   👁 Type, draw, image
   

   • A. Type: use your keyboard to write down your signature.
   • B. Draw: handwrite your signature using your mouse, or use your finger or a stylus pen on a touch-screen device.
   • C. Image: insert an image or picture with your signature to the document.
   • D. Descriptive alt text will be added automatically, but you can edit this at any time. The description will also be used as the name of your saved signature.

If the Save signature box is checked, your signature will be saved for re-use in the Add signature menu. You can remove it or add new signatures to PDFs at your convenience.

Merge PDF files

Firefox’s built-in PDF viewer lets you merge another PDF into the document you currently have open. This makes it easier to combine related files into a single PDF without using a separate application.

Merge a PDF into an open document

1. Open a PDF file in Firefox.
2. Open the page sidebar on the left side of the viewer, if it is not already open.
3. Click the + (plus) button in the upper-right corner of the sidebar.

   👁 mergepdf
   

4. In the file selection window, choose the PDF file you want to add.
5. Click Open (or press Enter).

The selected PDF is merged into the current document. You can:

• Save the merged PDF as a new PDF
• Scroll through the newly added pages
• View and navigate pages from the sidebar
• Continue editing or organizing the combined document

  👁 mergepdf1
  

Organize and split PDF files

With a PDF file open in Firefox, you can change the page order, copy, and delete one or more pages; you can also export pages into a new PDF.

Select the 👁 fxpdfsidebaricon
icon (top left) to open the left sidebar. Select one or more pages to:

• Reorder by dragging and dropping or
• Reorder by selecting Manage, then Cut, then Paste to insert them anywhere in the PDF.
• Copy by selecting Manage, then Copy, then Paste to insert. The original pages will remain.
• Delete by selecting Manage, then Delete or Cut. Select Undo to put pages back in their most recent location.
• Export by selecting Manage then Export selected…. Use the “Save As” pop-up to create a new PDF document containing only the pages you chose. The original file will remain the same.