JoAnn Paules [MSFT MVP] wrote...
Excellent advice, David! But of course, no one ever wants to actually pay
for such services.
....

And how many computer shop employees know how to remove passwords from
Office documents?

How many computer shop employees know how to tell whether person A has
legal standing to open any particular file? Now specialists in the
field would because they'd know their livelihoods depended on it, but
the average 24-year-old selling iPods and blank CD-Rs?

Are either you or David familiar with how easy it is to make any file
appear to below to any person? A could open a password-protected
computer file in a hex editor then save it to a harddrive or network
drive, thus changing the file ownership information. For files under
64KB, Windows still provides DEBUG.COM which can be used to do this.
Nuts, A could simply e-mail the file to himself from a web mail account
(which won't provide any ownership tags Outlook/Exchange might) and
detach the received copy. Granted the creation and modification dates
would be the same (a dead give-away), so use a touch utility a day or
so afterwards to change the access and modification times. How would
the proverbial computer shop employee be able to tell anything?

But at least you recognized the issue of cost, which was the OP's
original concern.