How to Sign a PDF on Mac — 4 Free Methods

Updated March 9, 2026 • 6 min read

Someone sends you a contract or form and asks for your signature. You're on a Mac. You could print it, sign it with a pen, scan it back in, and email it. Or you could do the whole thing digitally in about 30 seconds. Here's how.

Method 1: Preview (Best Built-In Option)

Preview is the unsung hero of macOS. It opens PDFs by default and has a signature tool that most people never discover.

  1. Open your PDF in Preview (double-click the file)
  2. Click the Markup toolbar button (pen icon) or go to View then Show Markup Toolbar
  3. Click the Signature button (looks like a cursive signature)
  4. Create your signature using one of three methods:
    • Trackpad: Sign with your finger on the trackpad
    • Camera: Sign on white paper and hold it up to the camera
    • iPhone: Sign on your iPhone screen (if nearby and on the same Apple ID)
  5. Click your saved signature to place it on the document
  6. Drag to position and resize as needed
  7. Save the file (Command+S)

The camera method is surprisingly good. Sign your name on a piece of white paper, hold it up to your Mac's camera, and Preview captures a clean digital version with the background removed. The signature saves in Preview for reuse — you only need to create it once.

Preview's signatures sync across your Apple devices via iCloud, so a signature created on your Mac also appears on your iPad and iPhone in Markup.

Method 2: Browser-Based Signing (No Software)

If you want a dedicated signing experience with more options, browser-based tools work great. Our PDF signing tool lets you:

  • Draw a signature with your mouse or trackpad
  • Type your name and choose from signature-style fonts
  • Upload an image of your signature
  • Place signatures precisely on any page
  • Add dates and text alongside your signature

Everything processes in your browser. The PDF never leaves your Mac. This matters if you're signing NDAs, contracts, or other sensitive documents — you don't want them uploaded to someone else's server.

Method 3: Quick Look (Fastest)

This is the method for when you're in a rush:

  1. Select the PDF in Finder
  2. Press Space to open Quick Look
  3. Click the Markup button at the top
  4. Add your signature (same as Preview's signature tool)
  5. Click Done

Quick Look uses the same signature library as Preview, so any signature you've previously created is available. This saves the step of actually opening the file in a full application. From Finder to signed in under 15 seconds.

Method 4: Using Mail App Directly

If someone emailed you the PDF and you want to sign and send it back without ever saving it locally:

  1. Open the email in Mail
  2. Hover over the PDF attachment
  3. Click the dropdown arrow and select Markup
  4. Add your signature
  5. Click Done — Mail creates a reply with the signed PDF attached

This flow is slick. Open email, sign, reply. No file management, no downloads, no scanning. It's exactly how PDF signing should work.

Are Digital Signatures Legally Valid?

In most countries, yes. The US ESIGN Act, the EU eIDAS regulation, and similar laws in Australia, Canada, and the UK all recognize electronic signatures as legally binding for most documents. A signature created in Preview or a browser tool qualifies as a Simple Electronic Signature.

Exceptions exist: some government forms, certain real estate transactions, and specific legal documents may require wet signatures or qualified digital signatures with certificate-based verification. But for contracts, agreements, invoices, and forms, digital signatures are perfectly legal.

Tips for Better PDF Signatures

Use the camera method for the most natural look. Sign on paper with a dark pen, hold it up, and Preview captures something that genuinely looks like your signature. The trackpad method tends to look shaky.

Sign in black ink for the paper version. Blue ink might not capture as clearly against the white paper.

Delete old signatures you don't use. In Preview's signature panel, hover over a saved signature and click the X to remove it. Keep only your current signature for security.

Flatten after signing if sharing widely. A flattened PDF embeds the signature into the document permanently, preventing anyone from moving or removing it. Without flattening, signatures exist as a separate annotation layer.

Add the date. Many signed documents need a date next to the signature. Use the text tool in Preview (T button in the Markup toolbar) to type the date, then position it next to your signature.

Signatures vs. Digital Certificates

What we've covered are electronic signatures — visual representations of your agreement to a document. Digital certificates are a step above: they use cryptographic keys to verify your identity and detect if the document has been modified after signing.

For most people and most situations, electronic signatures are sufficient. Digital certificates are typically used in corporate environments, government submissions, and high-value legal documents. If someone asks for a "digitally certified" signature, they're asking for something different from what Preview provides.

Our PDF encryption tool can add password protection to signed documents if you need an extra layer of security when sharing sensitive signed files.