Part IV: Managing and Analyzing Data
If Excel identifies items in the Document Inspector, it doesn’t necessarily mean that they should be removed. In
other words, you shouldn’t blindly use the Remove All buttons to remove the items that Excel locates. For example,
you may have a hidden sheet that serves a critical purpose. Excel will identify that hidden sheet and make it easy for
you to delete it. To be on the safe side, always make a backup copy of your workbook before running the Document
Inspector.
Two other commands are available in the File ➪ Info ➪ Check for Issues menu:
Check Accessibility Checks the workbook for content that people with disabilities might
find difficult to read
Check Compatibility Checks the workbook for the presence of features that may not work
in previous versions of Excel
See Chapter 6, “Understanding Excel Files and Templates,” for more about checking file compatibility.
Using a digital signature
Excel lets you add a digital signature to a workbook. Using a digital signature is somewhat
analogous to signing a paper document. A digital signature helps to ensure the authentic-
ity of the workbook and ensure that the content hasn’t been modified since it was signed.
After you sign a workbook, the signature is valid until you make changes and resave the
file.
Getting a digital ID
To sign a workbook digitally, you must obtain a certificate from a certified authority that is
able to verify the authenticity of your signature. Prices vary, depending on the certificate-
granting company.
Signing a workbook
Excel supports two types of digital signatures: a visible signature and an invisible
signature.
To add a visible digital signature, choose Insert ➪ Text ➪ Signature Line ➪ Microsoft Office
Signature Line. The Signature Setup dialog box appears, and you’re prompted for the infor-
mation for the signature. After you add the signature box, double-click it, and the Sign
dialog box appears; here you actually sign the document either by typing your name or by
uploading a scanned image of your signature. After signing the document, it will be marked
as final. Any change to the file will invalidate the signature.
To add an invisible digital signature, choose File ➪ Info ➪ Protect Workbook ➪ Add a
Digital Signature. If the signed workbook is changed in any way, the digital signature is
invalidated.
