If you knew that someone was looking at someone else's private documents, should you tell?

Question

It seems easy, as I write the question, that I should tell, but the information that was passed onto me, unsolictated, was of no huge consequence, and by telling the person, whose personal documents were looked at, I would cause much kerfuffle and animosity between the persons involved.
At the moment I feel "when in doubt, do nought".

Answer 1

Depends upon what the "personal documents" are, the relationship between the two people, the relationship you have with both of them etc. So, you didn't give enough information for an adequate answer.

Answer 2

It's really up to you. You do whatever feels right, but if this person is a family member, don't do it.