What's the correct way to fold A0 size documents or maps?

Question

What's the correct way to fold A0 size documents or maps?

Answer 1

Fold in half across the width.  This will get you back to A1 size.

Assuming you want to end up with an A4 size, then fold twice along the length (I do it concertina fashion for an A1 sheet - that way, with a bit of forethought, I can fold it so that eventually the title panel is on the outside).

This folded sheet will have the width equivalent to the length of an A4 sheet, but four times as wide.  Then you can fold it twice across the width, to end with an A4 sheet size, 32 sheets thick.

That's the thing with standard sheet sizes - folding in half either way will always provide you with a way of ending up with a smaller size.