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Firefox includes a built-in PDF viewer that lets you view and edit PDF files directly in your browser. This article will show you how to use the built-in PDF viewer and how to resolve common issues.

To learn how to switch to another PDF viewer, see Choose your preferred PDF viewer in Firefox.

Use Firefox’s built-in PDF Viewer

Firefox’s built-in PDF viewer allows you to view almost all PDF files found on the web without needing an external application (exceptions include PDF files with an incorrectly set MIME type). The built-in viewer is automatically used when PDF files are set to Open in Firefox in your Firefox settings for different types of files, which is the default setting. When you click a link to a PDF file or open it from the Firefox Downloads panel, it will open with the built-in PDF viewer.

The PDF file will open directly in Firefox without being saved. To save the PDF to your computer, click the Save button in the PDF viewer’s toolbar.

Fill out forms in PDF Viewer

Some PDF files have interactive fields to fill in data (such as on forms). Using Firefox's built-in PDF viewer, you can fill out fields such as text, check boxes and radio buttons. After entering data into these fields, you can download the file to have the filled-out version saved to your computer.

View document thumbnails or outline: The slider button on the far left will open a sidebar with thumbnails of the document's pages. Some documents will also have an outline view available. These make it easy to navigate through a long document.
Page up and down or skip directly to a page: You can use the up and down arrows to page through a document or enter the number of the page you want to go to.
Change the size of the document: Use the + and − buttons to zoom in and out, or choose a zoom setting from the dropdown menu.
Print: Click the Printer button to open the print setup dialog.
Save: Click the Save button to download and save the PDF file to your computer.

Edit PDF files

Editing a PDF allows you to add notes, highlights and other markings directly on the document. This is especially useful for making corrections, highlighting important information, or adding personal notes for future reference.

Click to choose a color and text size before selecting where on the document you wish to add text.
Click to choose a color, thickness and opacity before then being able to draw on the document. Downloading the file saves a copy of the document with your annotations.

Highlight in PDF files

Add a highlight

To highlight text or an area in a PDF document, first select the desired text or area. Then, click .
Choose your preferred highlight color, and adjust the thickness of the highlight.

Show/hide all highlights

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

Edit or delete a highlight

Click the area you previously highlighted.
To change the color of your highlight, click and select a new color.
To remove the highlight, click .

Comment in PDF files

Create a comment

To add a comment in a PDF document, first select the desired text or area. Next, click .
Type your comment, then click Add to save it in the PDF.

Edit a comment

Click to open comment editing, either:
- In the PDF, to open a single comment
- Or from the top right menu to see all comments in the sidebar and click to open one.
Click the Edit comment button.
Type your changes, then click the Update button

Delete a comment

Click to open comment editing, then click the Remove comment button.
You can click the Undo button right after you delete a comment to bring it back.

Useful tips

You can drag and drop the comment to a new location.
To see and manage all comments in a PDF, open the comment sidebar. In the upper right menu, click .

Add an image to PDF files

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

Insert an image

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

Reposition and resize the image

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

Add Alt Text for accessibility

After adding the image, click the + Alt text button.
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.
Click the Save button to insert the alt text.

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

Add a signature to a PDF

This feature is experimental and is being introduced to the Firefox user base through a progressive rollout. It may not yet be available to all users.

Warning: Signatures added using the Firefox PDF viewer are not legally binding e-signatures. They are simple annotations and do not provide authentication or verification.

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

Open the desired PDF in Firefox.
In the top right corner of the page, click the Add signature button and then click + Add New Signature.
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 option.
- 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.

PDF Viewer keyboard shortcuts

Command	Shortcut
Next page	N or J or →
Previous page	P or K or ←
Zoom in	Ctrl + +Command + +
Zoom out	Ctrl + −Command + −
Automatic Zoom	Ctrl + 0Command + 0
Rotate the document clockwise	R
Rotate counterclockwise	Shift + R
Switch to Presentation Mode	Ctrl + Alt + PCommand + Alt + P
Choose Text Selection Tool	S
Choose Hand Tool	H
Focus the Page Number input box	Ctrl + Alt + GCommand + Alt + G

Troubleshoot problems with the PDF viewer

With certain types of PDF files, the PDF Viewer may have problems displaying fonts, colors or the whole document. If some PDF files don't render well or are blank, click the download button on the right side of the document header to open it with the default PDF viewer application on your computer.
If you can't open any PDF files with the built-in PDF viewer, a Firefox extension could be the cause. You can disable all of your extensions, to see if one of them was the problem. For details, see Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems.

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View and edit PDF files using Firefox’s built-in viewer

Table of Contents

Use Firefox’s built-in PDF Viewer

Fill out forms in PDF Viewer

Edit PDF files