This question has been posted many times but not answered. The deskew in tools for Acrobat X Pro does not work as did older versions. My last version was Acrobat 8. The Document-optimize would straighten all received documants except locked. This is crucial for PDF documents received via mechaical fax. Almost everyone needs to be straightened. Sounds like the deskew now only works for locally scanned documents. A serious loss of that is the case.
Can you expand upon your workflow a bit? Are you scanning documents directly into Acrobat X using the Create > PDF from Scanner command or are you opening TIFF files and converting them to PDF? Deskewing can be invoked from several different command within Acrobat.
Thanks for letting us know. If you're opening TIFF files you can also invoke the Deskew under the following preference Edit > Preferences > Convert to PDF > TIFF and select the Edit Settings ... button. Under the Settings button you can turn the Deskew on or off.