Adobe Acrobat Pro Spell Checker does not work - Finds no misspelling

Spell checking (Edit - Spell Checking) does not work in Adobe Acrobat Pro X 10.1.1 on Mac OS X 10.6.8. Checking any document in any language always indicates:

"Spell check complete. No misspellings found"

Yet, there are many misspellings. Even tested with a PDF file created for that, filled with wrong words. Acrobat spell checking says they are all OK, yet they are all wrong.

Similar to this:

Spell Check in Acrobat 8 and Reader 8

http://acrobatusers.com/forum/forms-acrobat/spell-check-acrobat-8-and-reader-8

How to fix it?

Thanks.