From level 4 onwards he is intelligent enough to check the product of the station he is located in before flying to other stations to trade, avoiding empty trade runs.
From level 7 onwards he will recognize the chance to make a profit if the selling price is above the buying price. Before he only bought wares where the selling price was above average price.
From level 9 onwards the pilot will steer his ship to the closest shipyard if it has been damaged.
Additionally from level 8 onwards the pilot is able to check neighbouring sectors for good trade opportunities. This requires you to start the "Universe Trader" command (assuming you meet the other requirements below).
Level 8 allows the trader to use the jump drive, if the ship is not equipped with a jump drive the pilot will simply order one as soon as he reaches level 12 (at a 10% premium for delivery). Additionally the trader will order up to 12 Fighter Drones over time which he will use in emergencies to distract attackers.
If a Trader is attacked he will tell you the ID of the attacker so you know who to look for should you feel the need for revenge.
The jump distance for buying and selling increases with the Trader achieving higher levels until the ship covers nearly the whole universe. For reasons of rationality the buying-range is limited to a max. of 5 jumps (level 21+) otherwise the ship would require too much jump energy.
Up to level 12 the selling-range is 1 sector - the pilot is learning to check his neighbourhood.