Best preservation of parma ham?
To best preserve it's texture, especially that slightly moist part a good ham is supposed to have, I've found wrapping cured meats in plastic foil and keeping them in the fridge at a temperature where there is little condensation (not extremely cold, but you have to know your fridge) works for a decently long time (couple of weeks at least, if not months).

However things wrapped in plastic in the fridge tend to get moldy over time, there is no escaping that. And dried salted meats are after all a product of ancient preservation techniques. So if you really need it to last storing it in a dark and a bit chilly area, wrapped in a clean dry cloth or paper it should also stay good for long, although it will dry up some after it is cut and not vacuum sealed.

Last option is to wrap it in some paper and leave it on the bench. The paper should protect against dust and moisture, but at that point I would suggest that just eating it is a better way of storing it if it is a really good piece you spent some effort in acquiring.