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By Claudia McCue |

How to Sign a Digital Document: Know Your Options


When you put pen to paper to sign your name to a contract, personal check, or credit card receipt, it’s the equivalent of saying “I consent to this.” Your unique handwriting (or, in my case, unique scrawl) serves as the confirmation that you—not someone else—have signed the document.

When you enter the realm of digital documents, the options for signing become a bit more complex. Some companies accept Acrobat’s digital signatures, but some are uncomfortable with anything that doesn’t look like tasteful blue-black ink. I’ll show you how to sign a digital document to appease both camps.

What signatures can do

In addition to serving as proof that the intended recipient has viewed and approved a document, Acrobat’s digital signatures can be used to lock forms to prevent tampering after they’ve been signed. Even if you don’t use this option, a digital signature can indicate if a document has been altered after it was signed, and can provide a “snapshot” of the state of the document when it was signed, so you can see the post-signature alterations.

Creating a digital ID

When you click in a signature field in a PDF, you’re asked whether you want to use an existing digital ID or if you’d like to create a new one. If you don’t yet have a digital ID, click “Next” to start creating your digital signature.


Fill in your name and email address (the other fields are optional).


Next, assign a password (note: you’ll be graded on the security level of your password). When you click “Finish,” Acrobat is ready to sign the document.


Acrobat displays the default signature appearance: your name plus the signing date (down to the second), organization, and your email address, with the Acrobat logo as a watermark. But what if you want something that carries the security of a digital signature, with the look of a conventional hand-written signature?

You can create multiple digital IDs, and each digital ID can have multiple appearances. In the Appearance dropdown menu, choose Create New Appearance.


Just scan your signature and save the scan as a PDF (other formats won’t be recognized). If you want to eliminate other components of the signature, such as Location or Reason, just uncheck them under Configure Text.


Although this looks like a simple handwritten signature, it still has all the power of a digital signature.


Locking a file with a digital signature

When you create a digital signature field, you have three choices for what happens once the signature is affixed: nothing happens, certain fields (or all fields) are locked, or JavaScript code is executed. If you choose the locking option, be sure to warn users so they aren’t blindsided by signing before they’ve checked their entries, then discovering that they can’t fix any errors.


Even if you don’t select the locking feature, adding a signature brands the document as validated, provided that nothing is altered after the signature is applied.


What happens if someone changes the content of a field after signing the document? In the blue bar at the top of the document window (and in the Signatures pane), Acrobat warns you that the current signature is not valid—the document has changed since signing. But what has changed? This is pretty cool: The original state of the document is still available via the Click to view this version link.


Acrobat displays the original signed document, with a greenish-yellow band across the top to identify it as such. To see the differences, choose View > Compare Documents. It might seem odd, but choose the “Scanned documents” option. Acrobat generates a new PDF highlighting the differences between the original signed document and the altered version—it’s a great way to find even small differences.

Compare the current state of a PDF to the signed version to see if it’s been altered.

Compare the current state of a PDF to the signed version to see if it’s been altered.

Limitations on tablet devices

While tablets are taking over some of the tasks traditionally performed on desktop or laptop computers, the PDF viewers for tablets don’t necessarily support every feature of PDFs, especially digital signatures. While a user can scribble a name, when the file is returned to Acrobat Pro, the scribble isn’t recognized as an official signature, because none of these apps can create an official digital ID.

Even Adobe Reader for iPad doesn’t recognize signature fields. However, the annotation tools include a pen with instructions to “tap where you want to add your signature.” When the file is then opened in Acrobat Pro, the signature is a flattened annotation, and the document is regarded as unsigned.

PDF Expert for iPad recognizes the signature field and allows you to sign in the field, but Acrobat Pro regards the result as “Signed by Unknown,” and does not regard the signature as valid.

PDF Reader Pro for iPad doesn’t recognize the signature field; you can write with your finger or a stylus, but Acrobat Pro regards the signature as a Pencil markup, and sees the file as unsigned.

Limitations on non-Adobe viewers

Because the PDF specification is published, any software developer is free to create applications that view, print, and edit PDFs. One of the most common non-Adobe PDF viewers is Apple’s Preview, which takes a novel approach to signing—write your name on a piece of paper, then hold it up to your webcam for capture. Preview applies the signature graphic, but in doing so, deletes the signature field. Consequently, Acrobat Pro regards the file as unsigned.

Using Adobe EchoSign

If you have no control over what software (or device) your recipients will use to view and sign your PDF, consider Adobe EchoSign. This very flexible service accepts documents in a wide range of formats, including PDF, Microsoft Word, Excel, JPEG—even WordPerfect. Just submit files via a web browser from your hard drive, or directly from Google Drive, Box.net, Dropbox, or Evernote. Recipients just click a hyperlink in an email and sign, and it doesn’t matter what device or platform they use. Pricing starts at $14.95/month for a single-user account, but you can try the service free for 14 days.

Now that you know how to sign a digital document with Acrobat’s digital signature features, you’ll be better prepared to trade that ballpoint pen for its digital equivalent—happy signing!

For more tips on Acrobat, see my course Up and Running with Acrobat XI.

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