Global page sizes fit perfectly in both US and Metric paper sizes, without scaling.
If you or your collaborators use both US and Metric paper sizes, and you want to be able to print your proof documents, you should consider using Globally Compatible page sizes. These sizes are a tiny bit smaller than the standard one you currently use, but they print at 100% scale regardless of using a US or Metric paper size.
There are 2 Globally Compatible page sizes that are most useful for type design:
Fits both A4 and US Letter without needing to shrink
11in × 8.27in 279.4mm × 210mm 792pt × 595.28pt (ok to round to 595pt)
11 inches × 210 millimeters — the 11in “long side” of US Letter and the 210mm “short side” of A4
Only 0.23in shorter than US Letter and 17.6mm shorter than A4
Fits both A3 and Tabloid without needing to shrink
16.54in × 11in 420mm × 279.4mm 1190.55pt × 792pt (ok to round to 1191pt)
420 millimeters × 11 inches — the 420mm “long side” of A3 and the 11in “short side” of Tabloid
Only 0.46in shorter than US Letter and 17.6mm shorter than A3