This is a technique that I've used in my latest layout titled "Future" in my family gallery.
I've had this pattern paper with some designs of wood grain on it but the colours on it looked too flat. I wanted to do something to it so that it will looked more interesting and with an obvious texture on it.
I've used my distress ink stamp pad and inked it randomly onto the pattern paper. I've inked it a few layers so that I'm able to create different tones of it. This is a very simple way of adding some textures looked onto your pattern papers.