What additions to an interior ceiling can reduce noises of creaking / pacing from apartment above?
Unfortunately, the best solution to this would be a proper underlayment between the flooring and sub-floor in the above apartment.

If the apartment is old, it may not have any substrate to speak of.  If it was flipped specifically to be used as a rental, the contractor probably went with the cheapest material available.

If you were redoing your apartment you could look into sound-reducing insulation for the ceiling.  However, much of what you are hearing would be transmitted through the joists anyway, so this would not completely solve the problem.

https://www.soundproofcow.com/product/quiet-batt-30-soundproofing-insulation/