How to Sign a PDF on Mac — 4 Free Methods (2026)

Signing a PDF on a Mac is easier than most people realise — and you don't need to buy Adobe Acrobat or print anything. Mac users have several solid free options, ranging from the built-in Preview app to browser-based tools that also store your documents securely. Here are the four best methods with step-by-step instructions.

Method 1 — PrimeDocu in Safari (Best Overall)

PrimeDocu lets you sign a PDF entirely in your browser, which means no software installation, no updates to manage, and your signed documents are saved in an end-to-end encrypted vault. This is the best overall option for most Mac users because it combines a polished signing experience with serious document security.

1. Open Safari (or any Mac browser) and go to www.primedocu.com/home. Register for a free account — no credit card required.
2. Click Upload and select the PDF from Finder or drag it onto the upload area.
3. Click the Signature tool in the editor toolbar. Choose to draw with your trackpad, type your name in a cursive font, or upload an image of your handwritten signature.
4. Click and drag the signature to the correct position on the document. Use the corner handles to resize it.
5. Click Save. The signed PDF is stored in your encrypted vault. Download it or share a secure link at any time.

Because PrimeDocu is zero-knowledge encrypted, your key is generated on your device and stored in the macOS Keychain — it is never sent to PrimeDocu's servers. This makes it meaningfully more private than tools that store your documents in a standard cloud.

Method 2 — macOS Preview (Built-in, No Account Needed)

Preview is Apple's built-in PDF viewer and it has a surprisingly capable signature tool that most Mac users overlook. It doesn't require any account or internet connection, which makes it useful when you're offline or want a completely local workflow.

1. Double-click the PDF in Finder. It should open in Preview by default. If it opens in another app, right-click it and choose Open With → Preview.
2. In the toolbar, click the Markup toolbar button (the pencil-tip icon), then click the Signature button (looks like a cursive signature).
3. Choose Create Signature. You can sign using your trackpad (sign with your finger), your Mac's camera (hold a piece of paper with your signature up to the camera), or your iPhone or iPad if it's nearby (Continuity Camera).
4. Preview saves the signature. Click it in the Signatures menu to place it on the document, then drag and resize it to fit.
5. Press Cmd+S to save the PDF in place, or File → Export as PDF to create a new copy.

Preview is ideal for quick, one-off signings where you're comfortable with local storage and don't need encrypted cloud backup.

Method 3 — PrimeDocu Desktop Web

This is functionally the same as Method 1 but worth calling out separately for users who want to work with a larger screen layout. On a 13-inch or larger MacBook, the full PrimeDocu web interface gives you a side-by-side view of the document and the toolset, which is particularly helpful when placing signatures on multi-page contracts.

The steps are identical to Method 1. The free plan supports unlimited PDF signing with no watermarks, and the Pro plan ($9.99/month) adds 100 AI credits you can use to summarise or query any document in your vault.

Method 4 — Adobe Acrobat (Free Tier)

Adobe Acrobat's website (acrobat.adobe.com) offers a free e-sign tool that works in any browser on Mac. It is well-designed and handles complex PDF forms reliably. However, the free tier is limited in the number of signings per month and Adobe stores your documents on its own servers.

1. Go to acrobat.adobe.com and sign in with a free Adobe account.
2. Click E-Sign, then upload your PDF.
3. Click where you want to place the signature field, draw or type your signature, and click Apply.
4. Download the signed PDF.

Adobe's tool works well but is better suited to users who are already in the Adobe ecosystem. If you exceed the free monthly limit, you'll need a paid Creative Cloud subscription. PrimeDocu's free plan has no monthly signing limit.

Comparison: Mac PDF Signing Methods

Feature	PrimeDocu	macOS Preview	Adobe Acrobat
Cost	Free (unlimited)	Free (built-in)	Free (limited/month)
Software to install	None — browser only	None — built in	None — browser only
Signature options	Draw, type, upload image	Trackpad, camera, iPhone	Draw, type
Watermark on free plan	None	None	Possible on some actions
Encrypted cloud storage	Yes — AES-256-GCM	Local only	Adobe cloud (not E2E)
Account required	Yes (free)	No	Yes (free Adobe ID)
Best for	Most users	Offline / quick signing	Adobe users

Which Method Should You Choose?

If you want the best combination of quality, security, and convenience, PrimeDocu is the clear recommendation. It works in any Mac browser, adds no watermarks, stores your signed documents in an encrypted vault, and is completely free to start. If you need a purely offline solution with no account, macOS Preview is excellent. Adobe Acrobat is a fine fallback if you're already in that ecosystem and don't need more than a handful of signings per month.

Frequently asked questions