I do line-by-line proofs of formatted text against original manuscript. This includes checking the accuracy of headers, footers, and folios, and looking for bad line breaks and page breaks. I insert or check, as necessary, all page cross-references in the table of contents and throughout the manuscript.
I also do “cold” reads of the final proof of a manuscript I have not edited or proofread. Providing a fresh set of eyes is a valuable final check for typographical or formatting errors.