THIS IS NOT LEGAL ADVICE AND MAY CONTAIN FACTUAL ERRORS WITH RESPECT TO THE LAW. PLEASE CONTACT A LAWYER SPECIALIZING IN COPYRIGHT FOR LEGAL ADVICE.
Normally we don’t answer legal questions here but I think this one is simple enough to give basic context.
Music in the public domain may be used by anyone for any purpose. Want to arrange JS Bach 24 preludes and fugues for tuba / piccolo duet and sell it? Sure, go ahead.
Grey Area: Specific print editions of “unaltered” music. My understanding is that if a company creates a unique edition of the music, they would then own the copyright on that specific edition of the music. Okay so what does that mean?
Essentially it means that if you photocopied that specific edition and tried to sell the photocopies as your own work, that would be bad. But, if you used that edition as a springboard to creating your own edition and selling that, that would be fine, since it would be almost impossible to source exactly where you got that version of the material - due to its public ubiquitousness - and since it is public domain, people aren’t exactly going to be on the prowl.
Again, this is not legal advice. I’ve studied US Copyright Law a bit. This answer should be taken as context only.