How to sign a PDF on a Mac

There are some rarely known about, but incredibly useful Paint-style tools available in Preview, macOS’s built-in image viewer. And as of macOS Mojave, these tools are now available when you use Quick Look to get a preview of an image or PDF, simply by pressing Command + Space when the file is selected.

The tools include the ability to add notes and simple marks, speech bubbles and shapes to any image you have open in Quick Look or Preview without any fuss: jpgs, tifs, pdfs and plenty more. One of those features is the ability to create and save a digital signature, and then apply this to any image or PDF. We’ve looked the simple Paint-like features in a separate article here – and we also look at how to edit PDFs on a Mac here.

The digital signature is probably the most useful of Preview’s Paint-style features. So let’s look at it in more depth. Here’s how to sign a PDF or other image document using Preview’s digital signature feature. We’ll also look briefly at how you can use a similar feature in Mac Mail.

How to create a digital signature on a Mac

If you need to sign a PDF you might think the only way you can do so is to print it off, sign it with a pen, and then scan it in again. Alternatively you might be ‘signing’ things by using a fancy handwriting-style font. But there is a better way. You can save your signature to your Mac and insert that when you need it. Here’s how:

Note, we’ll walk you through using Preview to do this, but once you’ve got everything set up you will be able to insert the signature from Quick Look without even open the Preview app!

1. Open Preview. Or just drag a file on to the Preview icon in the Dock, if it lives there. Alternatively, depending on the file type simply double-clicking on a pdf or other image file may open it in Preview by default.
2. Click the Markup Toolbox icon – the pen in a circle just to the left of the search field – to open the editing tools, if the toolbar isn’t open already.
3. You should now see the bar of editing features, starting with Text Selection on the lefthand end and including Sketch, Draw, Shapes and, seventh from the left, an icon that looks like a scrawled bit of handwriting. This is the Sign tool’s icon. Click it.
4. If you’ve created any signatures, they will be listed and available here, but you can also click Create Signature to make a new one, followed by Click Here to Begin.
5. There are two ways to create a digital signature: Trackpad, and Camera. Scribbling it on a trackpad is the quicker method (press any key when you’re finished, followed by Done). You can use a fingertip, but it’s more accurate if you use a stylus.
6. But we find it hard to be accurate and prefer to write a signature the old-fashioned way on a white piece of paper and then hold it up to the webcam. Try to hold it steady, and match the writing to the guide line.

Sign a PDF or other image file

Once you’ve got a signature saved in Preview it’s incredibly easy to add it to this or any other image file in future. As we said above, as of macOS Mojave you don’t even need to open up Preview to do so.

1. Open the image or PDF file that you want to sign in Preview (or initiated Quick Look by selecting the file and pressing Space).
2. Scroll to the area you need to sign – if there are multiple pages it pays to be on the correct page before you bring up the signature.
3. Open the toolbar and click on the Sign tool icon. Then just click once on the signature you want, and it’ll appear slap bang in the centre of the image. Drag it to the appropriate location.

How to delete digital signatures

Maybe we’re paranoid, but those who share a Mac with other people – particularly those you don’t know terribly well – might not want to keep digital copies of their signature saved in Preview. (And it does keep the signatures saved by default.)

Click the signature icon in the Markup Toolbox and hover your cursor over the one you wish to get rid of. An X will appear; click this to delete the signature.

Sign documents in Mail

We’ve shown how to create digital signatures in Preview, but there’s a similar feature in Mail. When Mac OS X Yosemite launched back in 2014, Mail gained the ability to sign documents, such as PDF forms, digitally.

It works almost exactly the same as in Preview. Click the Sign button in the Markup toolbar and Mail will ask if you want to write your signature by hand, using your mouse or trackpad. It can also use your Mac’s webcam to take a photo of your signature as well.

For more advice on using Mail for Mac, see our roundup of Mail for Mac tips.