Nice thought.

I've been in a position where I needed to compare two or more similar documents and it's no great trick and doesn't take long. It's easier if you have the documents in electronic form and can apply comparison software, but with hard copies all you need is a bright light. You can overlay one copy on another, put the bright light behind them, align paragraphs and see if anything doesn't align. It's easy and fast with differences showing through as shadowy characters.