Originally posted by bomber1392
so i dont copy the PARAM.SFO
Nope, you copy every file BUT the .SFO.
The .SFO contains your PSNID, which in this case says that save file belongs to another PSNID.
Now, if you didn't copy their .SFO and use yours your PS3 would think that the save is yours; thus you will be able to use the save to unlock trophies.