Talk to the boss of each camp camp, and in one option they'll talk about the paper. To get it, you have two options : either you have 3 allegiance point with the faction (but currently it needs some really specific actions for it), or you leave Illoia with them, you get a scene, and the paper.
Viewing post in Ballad of Outstanding Bimbo Sorcery comments
The bandit camp is in the complete north, on the lake (not the small lumber camp in the south east), and the boss is in the tavern, the biggest house. The entrace is between the two braziers, on the left, following the dirt path. I know a lot of people missed it (I've added small footprints in the next update to make it stand out more). The boss in on the bottom partof the tavern.