It is pretty simple really. If a person could access the word documents in a protected directory then a search engine could.
Search engines have no more access than anyone else would have. It is not like they have a magical key to read anything they want.
Some search engines might try to guess the password a couple of times (probably unlikely), but you would never see that on any major search engine... or public one really.
You also don't really mention what method of password protection this directory has.