If you need the password even to open the doc, then you're probably stuffed,
although I do believe you can pay to have the password cracked - probably
more than the doc is worth, though.
If however the password is to amend the doc, then copy and paste the whole
thing into a new doc and save that one over your original.
If you have any idea what the password was, then try misspellings of it,
strange capitalisation, and finally, try retyping it with caps lock on (in
case you didn't realise it was on when you set the password).
Hope this helps.
Tom.