Artificial atomic systems in solids such as single photon emitters are becoming increasingly important building blocks in quantum information processing and scalable quantum nanophotonic networks. Here, we report on a controllable way to engineer emitters in two-dimensional (2D) hexagonal boron nitride (hBN) crystals using plasma processing. The method is robust, and yields a 7-fold increase in the density of emitters in hBN, which is promising for their deployment in practical devices. While as-fabricated emitters suffer from blinking and bleaching, a subsequent annealing step yields photo-stable emitters. The presented process is the first step towards controllable placement of quantum emitters in hBN for integrated on-chip quantum nanophotonics based on 2D materials.