Really, the thing that mystifies me about this is that the Vatican simply didn't forge a letter. I mean, the reason that they are getting into hot water is that they redacted a letter to remove the parts that were contrary to the agenda that they wanted to push, and they did this quite clumsily with the books in particular (but I guess it must have been hard to find another way to simultaneously show the signature from Benedict without showing his closing remarks). And they were even willing to lie about reading the "full text" of the letter while still omitting details.
Thus it is apparent that they didn't mind using deception. But that being the case, why not just fabricate a letter out of whole cloth? Then you wouldn't need to cover anything up in your picture, and so would be far less likely to be caught in your deception. Maybe they didn't want to forge the signature, even if they were willing to distort the message, I don't know.
