How to Sign a PDF on Linux — 3 Methods

Signing PDFs on Linux: The Challenge

Linux users know the feeling. You receive a PDF that needs your signature, and you realize that the two most commonly recommended tools — Adobe Acrobat and macOS Preview — are not available on your operating system. Windows users have Adobe Reader. Mac users have Preview. What do Linux users have?

More options than you might think. This guide covers three reliable methods to sign PDFs on Linux, whether you are running Ubuntu, Fedora, Arch, Debian, openSUSE, or any other distribution.

Method 1: Browser-Based PDF Signer (Recommended)

The fastest and most straightforward method works on every Linux distribution because it runs entirely in your web browser.

How It Works

1. Open SigPDF in Firefox, Chromium, Chrome, or any modern browser
2. Upload your PDF by dragging and dropping it onto the page
3. Click "Add Signature" and draw your signature with your mouse or drawing tablet
4. Click on the PDF to place your signature where it belongs
5. Download the signed PDF

Why This Works Best on Linux

• Zero dependencies — No packages to install, no repositories to add, no dependency conflicts
• Distribution-agnostic — Works identically on Ubuntu, Fedora, Arch, NixOS, or any distro with a browser
• No Flatpak/Snap/AppImage complexity — Just a URL
• Wayland and X11 compatible — Since it runs in the browser, display server differences do not matter
• Privacy-friendly — SigPDF processes files in your browser. Nothing is uploaded to a server. For Linux users who value control over their data, this matters.

Best for: Anyone who wants to sign a PDF quickly without installing anything.

Method 2: LibreOffice Draw

LibreOffice comes pre-installed on most Linux distributions, and LibreOffice Draw can open and edit PDFs — including adding signatures.

Step-by-Step Instructions

1. Open a terminal and launch LibreOffice Draw:

   libreoffice --draw document.pdf
   

   Or right-click the PDF in your file manager and select "Open With > LibreOffice Draw"

2. The PDF will open with each page as a separate canvas. Navigate to the page that needs your signature.

3. To add a signature, you have two options:

   Option A: Insert a signature image

   • Go to Insert > Image
   • Select a PNG image of your signature (with a transparent background if possible)
   • Position and resize it on the signature line

   Option B: Draw a signature directly

   • Select the Freeform Line tool from the drawing toolbar
   • Draw your signature directly on the document
   • Adjust the line thickness and color as needed

4. Export as PDF: File > Export as PDF > Export

Pros

• Pre-installed on most Linux distros
• Full PDF editing capabilities beyond just signatures
• Works offline
• Open source

Cons

• The PDF rendering is not always pixel-perfect — complex layouts may shift slightly
• Drawing with a mouse using the freeform tool is awkward
• The export-as-PDF process adds extra steps
• Heavier than necessary for just adding a signature

Best for: Linux users who already use LibreOffice and need to make additional edits to the PDF content.

Method 3: Xournal++

Xournal++ is an open-source handwriting and annotation application that works well for signing PDFs. It is available in the repositories of most major distributions.

Installation

Ubuntu/Debian:

sudo apt install xournalpp

Fedora:

sudo dnf install xournalpp

Arch Linux:

sudo pacman -S xournalpp

Flatpak (any distro):

flatpak install flathub com.github.xournalpp.xournalpp

Step-by-Step Instructions

1. Open the PDF in Xournal++:

   xournalpp document.pdf
   

2. Select the Pen tool from the toolbar (or press P)

3. Draw your signature on the appropriate line in the document. If you have a drawing tablet, this will feel natural.

4. Adjust the pen size and color if needed (the toolbar has options for both)

5. Export the annotated PDF: File > Export as PDF

Pros

• Purpose-built for PDF annotation
• Excellent drawing tablet support (Wacom and others)
• Lightweight compared to LibreOffice
• Open source and actively maintained
• Works well on touchscreen Linux devices

Cons

• Requires installation
• Adds annotations as overlays rather than embedding in the PDF structure
• Not pre-installed on most distributions
• Learning curve for first-time users

Best for: Linux users with drawing tablets who frequently annotate PDFs.

Method Comparison

| Feature | Browser (SigPDF) | LibreOffice Draw | Xournal++ | |---------|-------------------|------------------|-----------| | Installation | None | Pre-installed | Package manager | | Speed | Fastest | Slow | Medium | | Signature quality | Good | Variable | Excellent (with tablet) | | Privacy | Client-side only | Local | Local | | Works offline | No | Yes | Yes | | Distro support | Any (browser) | Most | Most | | Best input | Mouse/touch | Mouse | Drawing tablet |

Command-Line Options

For Linux power users who prefer the terminal, there are some CLI-based approaches worth mentioning, though they are more complex:

Using ImageMagick + pdftk

You can overlay a signature image onto a PDF using a combination of ImageMagick (for image manipulation) and pdftk (for PDF assembly). This approach requires creating a separate PDF with just your signature, then stamping it onto the target document.

# Convert signature image to a PDF page
convert signature.png signature.pdf

# Stamp the signature onto page 1 of the document
pdftk document.pdf stamp signature.pdf output signed-document.pdf

This works but lacks precision in positioning. You would need to carefully size and position the signature image beforehand.

Using GIMP

GIMP can open PDFs and let you draw or paste a signature image, then export back to PDF. However, GIMP rasterizes the PDF (converts it to an image), which degrades text quality. This approach is generally not recommended.

Tips for Linux Users

1. Invest in a drawing tablet — Even a basic Wacom tablet makes digital signatures look much more natural. Linux has excellent Wacom driver support through the kernel.

2. Create a signature PNG — Sign a white piece of paper, photograph it, and use GIMP to remove the background. Keep this PNG file handy for inserting into documents.

3. Use keyboard shortcuts — In Xournal++, pressing P activates the pen and Ctrl+E exports to PDF. Learning shortcuts speeds up repeated signing.

4. Check your browser — For browser-based tools like SigPDF, Firefox and Chromium both work well on Linux. Make sure you are on a reasonably recent version for the best experience.

The Simplest Path

For most Linux users, a browser-based tool is the path of least resistance. No packages to install, no dependency chains to manage, no configuration files to edit. Open SigPDF in your browser, sign the document, and move on with your day.

Sign Your PDF Now →