PP has a really nice grain tool, but it's missing the "size" slider.
It's one of my favourite features to use when creating artwork and binding together different layers with different pixel densities.
It's also an important feature when emulating a lot of vintage photo effects. giving you that VSCO look.
![Image](http://pixelmator-support.s3.amazonaws.com/uploads-new/cuf_1526972524_GRAIN-s.jpg)