Can you transfer an item bought on one PSN account to another?

You can't.

At best you can have both accounts homed on that PS4, download the game from account #1, then logout and play from account #2. But account #1 still needs to be bound to that PS4. If you move account #1 to another PS4 then all of the games it had downloaded will be deactivated and account #2 will no longer be able to play them (you'll get an invalid licensing notice).

Unfortunately, you can't. For example, in COD, I can purchase the season pass on my dad's account and be able to play the maps on my account, but will not be able to access the DLC Gobblegums, as I techniclaly do not own it.