How to Set a Custom Lock Screen Message on a Mac

When you receive a contract, lease agreement, or tax form via email, the traditional workflow involves printing the document, signing it with a physical pen, scanning it back into the computer, and emailing it. This process is slow, wasteful, and entirely unnecessary if you use a Mac.

macOS includes a powerful, native PDF viewer called Preview. Buried within Preview is a highly sophisticated digital signature tool that allows you to capture your actual, handwritten signature and apply it to any PDF document in seconds.

Step 1: Creating Your Digital Signature

Before you can sign a document, you must digitise your signature. You only need to do this once; your Mac will save it securely in your keychain for future use.

1. Open the PDF document you need to sign. It should open in the Preview app by default.
2. Look at the top toolbar and click the Show Markup Toolbar button (it looks like a small pen tip inside a circle). A secondary toolbar will appear below the main one.
3. Click the Sign icon (it looks like a small cursive signature).
4. Click Create Signature.

You will be presented with three options for capturing your signature:

• Trackpad: Click the “Click Here to Begin” button, then use your finger to draw your signature directly on your MacBook’s glass trackpad. Press any key when finished.
• Camera (Recommended): Write your signature clearly on a blank piece of white paper using a dark pen. Hold the paper up to your Mac’s webcam. The software will instantly detect the ink, remove the paper background, and digitise it perfectly.
• iPhone or iPad: If your devices are synced via iCloud, you can select this option to use your iPhone or iPad screen as a drawing tablet, allowing you to sign with your finger or an Apple Pencil.

Once you are satisfied with the captured signature, click Done to save it.

Step 2: Applying the Signature to a PDF

Now that your signature is saved, applying it to any document takes just two clicks.

1. With the PDF open in Preview, ensure the Markup Toolbar is visible.
2. Click the Sign icon.
3. A dropdown menu will display your saved signature(s). Click the signature you want to use.
4. The signature will be dropped directly into the centre of the PDF page.
5. Click and drag the signature to the correct signature line on the document.
6. Click and drag the blue corners of the signature box to resize it, ensuring it fits perfectly on the line.

Once positioned correctly, simply close the document (or select File > Save). The signature is permanently embedded into the PDF, and it is ready to be emailed back.