QuarkXPress 8 and above has a Scale feature that can intelligently scale entire layouts or selected items.
Just choose Window> Scale and enter a percentage or absolute size. If you have any page items selected, it will scale those items. If you click the Layout checkbox, it will scale all the pages in the entire Layout instead.
For example, here’s how to scale a Layout from U.S. Letter (8.5″ x 11″) to A4:
We used these values for the new page size:
8.268″ or 21 cm
11.693″ or 29.7 cm
Tip: If you don’t want everything on the page to scale equally, you can control what gets scaled by opening the Scale Settings dialog — just click the icon in the upper right corner of the Scale palette.