A4 or Letter, without reprinting
Documents made in the United States usually use Letter, almost everywhere else uses A4. When a portal or a printer expects one of them, mixed sizes cause cut edges or odd margins. This page turns all pages into the size you choose in one step.
Scale to fit keeps the proportions and makes the content as large as possible on the new page. Keep size leaves the content at its real size and centers it, useful when the exact print size matters. A preview shows the result for the current page before you save.