Handy tip: because the ratio of the sides of all A size papers is root 2, or 1.41, it's always the case that expanding a document from one size to the next largest needs a factor of 141% dialled into your photocopier or typed into Illustrator or whatever. Reducing from one A size to the next smallest requires a factor of 1 over root 2, or 0.71, or 71%. Worth remembering those two numbers.
