As a translator, I also regularly proofread the work of others. It’s not always easy, sometimes it takes longer than if I had done the translation myself, although that is not the case very often. However, what amazes me is that way too often the translator in question seems to not even have taken (or maybe had) the time to run a spell check before submitting the translation. It’s such an easy thing to do, and the first step in all QA work I do, whether on my own translations or on someone else’s.
But of course, that doesn’t guarantee that there won’t be mistakes that are purely spelling or even grammar mistakes. After all, a spell checker is only a tool, not an intelligent human being. A wrong word, spelled correctly, is still the wrong word. If you leave out one, the spell checker won’t catch it.

Taylor Mali puts the pitfalls of blindly relying on a spell checker quite aptly in this little speech, not only for students: