In a recent article we looked at the simple Paint-like features that are included (but rarely known about) in Preview, macOS's built-in image viewer. You can add notes and simple marks, speech bubbles and shapes to any image you can open in 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.
The digital signature is probably the most useful of Preview's Paint features and we only had time to address it quite briefly in the previous article. 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 a similar feature in Mac Mail. We also have more tips for using Preview to edit a PDF on a Mac here.
Create a digital signature
Open Preview. It's easiest to drag a file on to the Preview icon in the Dock, if it lives there, although depending on the file type and how you've got your settings, simply double-clicking a pdf or other image file may open it in Preview by default. You can also do a Spotlight search for Preview, double-click the icon, find the file on your Mac and click Open.
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.
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.
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.
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.
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.
With the image file open in Preview, open the toolbar and click again 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.