How to Sign a PDF on Mac (Without Preview's Limitations)

macOS has had built-in PDF signing through Preview since OS X Lion. It works for the simplest case — sign a document yourself and send it back. The moment a workflow involves sending the document to someone else for their signature, Preview hits a wall. Here's the full picture.

Step-by-step: How to sign a PDF on Mac

1. Open the PDF in Preview — double-click the PDF in Finder; Preview is the default for PDFs on Mac
2. Click the markup toolbar icon — shaped like a pen tip; if you don't see it, click the icon that looks like a marker in the toolbar to reveal it
3. Click the signature icon and choose Create Signature — you'll see options for trackpad, camera, or iPhone
4. Create your signature — trackpad gives the most natural result; camera works if you sign on white paper and hold it up; iPhone Continuity works if both devices share an Apple ID
5. Drag the signature onto the document — click the saved signature in the dropdown and place it where you need to sign
6. Resize and reposition — drag the corners to resize; click and drag to move
7. Save the file — Cmd-S saves; the signature is now embedded in the PDF and travels with the file

If something goes wrong

• The signature appears blocky: Mac upscales low-resolution signatures; redo the signature using the trackpad for the cleanest result
• I need someone else to sign too: this is where Preview falls short — you'd email the file, they'd sign their copy, then send back, and you'd have no audit trail. Use a proper e-signature tool for any multi-party signing.
• The PDF is locked or password-protected: Preview can't sign protected PDFs without unlocking; obtain the password from the sender or use a tool that handles permissions
• My iPhone signature isn't syncing: make sure both devices are on the same Apple ID, both have Bluetooth and Wi-Fi enabled, and Continuity is active
• The signed file is much larger than the original: Preview re-encodes the PDF when signing; some bloat is normal but excessive growth suggests embedded high-res images

Other options

Different tools, different tradeoffs:

• Preview — best for self-signing a single document and sending the final PDF back. No audit trail.
• Adobe Acrobat — more features, certified signatures, but expensive subscription if you only sign occasionally.
• DottiSign — best for sending a document to someone else for signing, with audit trail and templates. Free tier covers casual use.

The fastest way

If you're going to be doing this more than once, save the setup as a template. The 30 seconds you spend saving it pays back the next time you need to do the same thing — which, in most cases, is sooner than you think.

Try DottiSign if you want the simple version: upload, drag, sign, done.