This achievement is probably one of the easiest "Dossier" achievements, as there is only one level in the Barcelona mission that you have to collect all the objectives for. Keep in mind, like it says in the achievement description, you must play this on 007 difficulty or higher. Also a nice thing about this game is you will see a little notification in the corner of the screen when you are close to your objectives.
There are 6 objectives in this level. 3 of them are unmissable (story-related) and 3 of them are missable (bonus objectives). To get the achievement you have to get all 6.
I'll only go over the bonus objectives because you can't miss the story-related objectives.
Obtain Zukovsky's contact list: After the scene where you talk to Zukovsky run into his office and on the right, you will see a multicolored picture of him. Shoot the picture and it will fly off the wall, revealing a hidden safe. Open the safe and take the contact list.
Photograph evidence of Zukovsky's arms deals: As you go through the level you will eventually get to a room before the big kitchen area. When you open the doors, two guys will come in the opposing doors, quickly kill them and take the door on the left. Kill the guy in that room and proceed through the door ahead and quickly kill the guy in that room and you will see a box with a lock on it with some guns inside. Take out your smartphone and photograph the box to the right of it.
Obtain the nightclub's security footage: This one was tricky for me because I kept noticed the smartphone's little notification telling me I was close-by to the bonus objective but I couldn't get in through the locked door and the vent beside the door didn't lead me to the room like I thought it would. So you eventually find yourself in a large lounge area with A LOT of enemies you have to fight. So once you are done killing all of them your main objective will tell you to go through a set of doors. Do not go through those doors just yet, go up the set of stairs on the right side of the room and a few more enemies should come through the door. Kill them, go through that door. There should be a vent that will lead you into the security room. Use your smartphone to photograph the last bonus objective in the security room.
Now all you have to do is finish the level and the achievement should pop.
Hopefully I covered everything, if you noticed I missed something. Comment/send me a PM and I will update the guide for you.