We had a discussion about this on Facebook a few months ago. If you size up you'll retain all of the detail that the original-sized model should have. Often you'll be ok going down, but it depends on your software and what kind of printer you are using. Other than that generalization, I'll defer to the experts on here!
Designer and owner of Forward March Studios: The World's first comprehensive range of 3D printed historic miniatures.
in my opinion you can print stl-files smaller and larger .... but only for a small range! 2mm is possible 1:1000 - 6mm 6mm is possible 2mm - 15mm 15mm is possible 6mm - 28/30mm some stl-files are in such a high quality that the range is higher - but you should test it!
6mm and smaller you should print with an Resin (SLA) Printer. (We start this soon - at the moment China couldn't deliver)
We print also with Prusa MK3S 2mm scale - it's ok, but a lot of work to prepare it for a pretty good painting scene.