Good catch, though the fix I don't think is quite right. "Proofread carefully to see if you [have left/are leaving] words out" probably should've been what I wrote. I invite a much more competent writer to fact-check me.

"Proofread carefully to see if you [leave] words out." I believe is grammatically correct but a bit nonsensical as I'm no longer in the act of writing words when I'm proofreading. But again, I'm also possibly just embarrassing myself at this point.