OP says he compared them in terms of KBs, if this is taken literally then he didn't check to see if they were exactly the same length. Assuming that the two word documents are actually identical except for metadata, I wouldn't expect the size discrepancy to be on the order of kilobytes.

Still a reckless way to identify the leaker, there's plenty of reasonable doubt if all they have to go on is the size of the document that was printed.