When linked up with Leia she will have the ability to steal items of the foes you are targeting that have been downed. Sometimes this will fail, if it does, you can simply knock the foe down again and keep trying until you get an item. Each foe can only be robbed once per battle.
I, personally, earned this during my second playthrough when I was way too high of a level to hope to earn this normally. It was because of this I used the following steps...
1.) Go to the Old Vicalle Mine and get the Aifread treasure in the second area in the NE part of the map. It should give you the ability to use the "Minimum Damage" skill. Once you earn this skill, place it on both Jude as well as Leia.
2.) Now, you'll be going down to the strategy part of the main menu. Don't worry about setting up anything for Jude and make sure Leia is set to "Focus Attacks" under targets. My other members were Alvin and Elize. I set them to "Only Heal" under action and put their links to prioritize healing just in case. Don't set up "Minimum Damage" on them.
3.) Now! You're ready to get in to a battle. You'll be playing as Jude and you'll want to set his arte "Aqua sweep" to one of your inputs (I went with the neutral position so I could simply press circle, your call). Once the battle begins, make sure you've linked up with Leia and run in and use the Aqua Sweep on the first enemy you see. It'll do 1 damage and should knock the enemy over. If Leia is behind them, she'll kneel down and try to steal from them. Progress through each enemy robbing them once and carry on.
4.) Once you've robbed them blind, hold L1 and press left or right on the D-Pad to switch to Alvin. Make quick work of your foes and repeat the process.
Having something that reduces the TP cost of Judes artes helps, otherwise you'll be using some recovery items along the way! At least that's progress towards your "Auto-Item uses". I personally chose to do this in the Kijara Seafalls but the location is yours to choose. If you aren't overleveled and just want to make progress towards the trophy, disregard the minimum damage and strategy bits and simply link up with Leia using Jude and his Aqua Sweep.