Just as a SwiftKey PSA...
In the event you open a document that is more than a page or two in length, it's likely that the app will grind to a halt, then totally freeze. If your doc is longer than that, I'd give it a 0% chance of working.
I realize that most people only type a sentence or two in their message apps and never use their phones for anything more involved. But some of us do. If you are in that camp, don't be surprised if SK freezes and stops working.
The rub is the way SK was designed. It's been this way for years, it's been reported a million times and the SK devs have never addressed this problem. Too bad. The app has a wonderful prediction engine.