NOTE: The words italicized below are assumed menu options available/steps to initiate the following actions, which are unable to be verified at this time with the person I am helping with this problem.
With a PDF that has had it's metadata removed (I presume that Acrobat has only one method of doing this) open, which was only ever opened on the one PC, in the one instance of Acrobat XI, selecting it's "Document" menu, then "Header & Footer", and then either "Update" or "Remove", leads to dialog boxes being displayed stating "Acrobat cannot find any headers or footers in this file. If you see header or footer information it was not added in Acrobat and cannot be detected as such." and (shown here with grey indicating the difference between the two) "Acrobat cannot find any headers or footers in this file. If you see header or footer information it was not added in Acrobat or by an Adobe PDFMaker, and cannot be detected as such.", respectively.
Has anyone else encountered this and has a fix, or does anyone known why Acrobat thinks it didn't add header and footer info it did (which presumably is the only issue preventing updating or removing them)?