Convert PDF to A3

A3 is 297 by 420 millimetres — exactly twice the area of A4 and sharing its 1:√2 proportions, which is the reason A4 content maps onto A3 with no leftover bands at all. Scaling an A4 page up to A3 multiplies both dimensions by roughly 1.414, so an 8-point annotation on a plan becomes an 11-point one and a hairline rule stays a visible line. That makes A3 the standard escalation for drawings, seating plans, posters and any document that was legible on screen but cramped on paper. Because the source page is embedded as a vector form object rather than rasterised, text and line work enlarge with no loss of sharpness whatsoever. Bitmap images are the exception: their pixel count is fixed, so a photograph printed at 141% of its original size has 141% larger pixels and correspondingly lower effective resolution. Centre mode instead leaves content at true size with a generous A3 border.