I had to have a copy of a legal document certified recently, and the certification
wasn't about the validity
of the copy at all. As a matter of fact, when I started to explain what the document was for, the office clerk protested, and said he didn't want to know anything about the contents of the document.
What he did do was look at the name and signature printed on it. The stamp he put on it certifies that they match with the ID shown to him (my passport).
So the certification only proves that the copy was actually in my possession. It's like a PGP key.