Free Spell-Checker, Grammar-Fixer
I have started using a free program called Grammarly. I like it.
As I type, it highlights spelling errors. It also highlights grammatical errors. Usually, it is correct. I ignore it when it isn't.
I still use a paid proofreader, but Grammarly makes his work easier.
Every so often, I get nagged onscreen to upgrade to the Pro version. Their ads have yet to explain satisfactorily what the advantage is.
It never hurts to have another pair of eyes, even if they are digital.