How to sign digital documents

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Reader Isabel Lorenzo has been asked to sign on the dotted line. She writes:

I’ve received some electronic documents that I’m supposed to sign. I could print and sign them and mail them back, but I’ve heard there’s a way to sign them right on my Mac. Do you know how it’s done?

You have a couple of options, Isabel. If you’re running Mac OS X Lion or later, you can take advantage of Preview’s Signature feature. Alternatively, you can use Adobe Reader. We'll start with Preview.


Launch Preview, open its preferences, and select the Signatures tab. Click the plus (+) button at the bottom of the window.

A Signature Capture window will appear and your Mac’s camera will light up. Scrawl out your John Hancock on a piece of paper, and place that paper before the camera so that the signature aligns with the blue line in the viewer area. Signature Capture will grab your signature and display it to the right of the viewer. Click the Accept button, and the signature will be added to Preview’s list of available signatures.

Capture your signature with your Mac's camera.

When you need to sign a PDF, choose Tools > Annotate > Signature. A crosshairs cursor will appear. Drag it, and your signature will appear. (If you’ve stored more than one signature, click the Signature menu in the toolbar and select the signature you wish to use.) Drag the signature where you’d like it to appear, and if necessary, resize it. Save the PDF, and your signature will be embedded in the document.

Adobe Reader

You can also slap a signature on PDF files with Adobe Reader . While Reader doesn’t offer Preview’s camera trick, applying a signature is pretty easy.

Open a PDF and click the Sign button that appears in the toolbar. Click the triangle next to the 'I Need to Sign' heading and choose Place Signature. In the Place Signature window that appears, choose Type my signature and enter your name in the appropriate field. Your signature will appear below in a script-like font. Click the Accept button, place your cursor where you’d like your signature to appear, and click. The signature will appear on the page, where you can then resize it.

My signature was never so neat.

If the recipient of your document is likely to respond with “I’ve seen your signature, and that ain’t it!” return to the Place Signature command and choose Clear Saved Signature. Now click Place Signature yet again and, in the window that appears, choose Draw My Signature from the first pop-up menu and then do your darndest to create a legible signature, scrawling it with your mouse or trackpad. Again, click Accept when you’re done and place the signature in the document.

This kind of signature is fine in some cases, but not all. For greater security, some documents (those with Adobe’s Reader Usage Rights enabled) must be digitally signed. Adobe Reader includes a feature for creating such digital IDs.

Launch Adobe Reader, open its preferences, and select Signatures. In the Identities & Trusted Certificates area, click the More button. In the window that appears, you’ll see a handful of certificates.

Click the Add ID button, and in the resulting window enable the A New Digital ID I Want To Create Now option and click the Next button. In the Add Digital ID window, enter your name and an email address. The Key Algorithm pop-up menu offers two options—'1024-bit RSA' and '2048-bit RSA'. The latter is more secure but the former is more widely compatible. Choose one and click Next.

In the subsequent window, you’ll see the location of your signature file. Make a note of it should you wish to back it up. Then enter and confirm a password. When you’re done, click the Finish button. Your signature will appear at the bottom of the certificate list. Click the Close button and close the preferences window.

When you next need to sign a document that requires a certificate just double-click in the digital signature field, and the Sign Document dialog box will appear. Enter the password for your signature and follow the instructions to insert your signature.

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