Order/Invoice Page Size

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I believe the Order and Invoice forms are set up with an A4 page size (8.26" x 11.69"). In the U.S., we user a Letter page size which is 8.5" x 11". Due to the extra length of the A4 page size, printing with scaling to fit the length is making the fonts small enough that clients find it difficult to read. Making the font larger won't help unless I can widen the left and right margins to accommodate the longer lines. In which case, just being able to choose a Letter page size solve the problem more easily. Is there a way to change the page size for printing?