I use spell checking and grammar checking – is that good enough?

No.

Spell checking and grammar checking are both useful automated tools. You can use them to help with your writing. Unfortunately, these tools do not understand everything about English. Sometimes they cause errors. Even if they offer valid corrections, your writing may become less accurate, potentially even dangerously so.

For example, if you type "pit" instead of "pat", "pet", "pot" or "put", spell checking will not correct it.

Another perfect example is if you intended to write "Do not drink this!" but instead you wrote "Do drink this!". Spell checking and grammar checking will not correct this mistake and the consequences could be disastrous.

Only an experienced human editor will find many of the mistakes in a document. A good editor will go further and make the writing flow and glow, giving life to your work in a way that automated tools cannot. Pure English editors will make your work shine brightly.