My colleage tried to create a PDF out of MS Word doc last week but MS Word crashed. She was asked to disable the PDFMaker plug-in from MS Word to solve the issue. After they did that, Word automatically recovered. However, the Acrobat tab was not displayed. She tried to add the plug-in back through Word Options>Add-Ins> COM Add-ins but the Acrobat tab was still missing. Both of them were running Office 2007 on Windows 7 (64b).
This week, after I upgraded my system to Windows 7 ((64bit)) and MS Office to Office 2010, I had the similar issue (Word crashed, Acrobat tab missing, and add-in failed to add back). Then I tried all methods listed here: http://helpx.adobe.com/acrobat/kb/pdfmaker-unavailable-office-2007-office.html, but the problem wasn’t solved.