This is the nuts-and-bolts edit.
Sometimes called proofreading*, it’s actually the final editing stage. I check that grammar/syntax/spelling/punctuation are correct, look for any discrepancies in the manuscript (for instance, page four says Mandy always has lunch at Rita’s Cafe, but page fifty mentions Rita’s Cantina).
(Easy Math for Writers: $300 per 50K words)
*While I proofread along the way, any revisions have a way of sneaking errors into a manuscript. I recommend a final round of proofreading for any document, preferably in its final formatted state.