As the final check before publishing, proofreading shouldn't require heavy manipulation of the text.
My approach includes the following:
Correction of errors in spelling, punctuation and grammar
Checking for typos
Adhering to house style where this is provided; otherwise ensuring consistent usage throughout document
Checking word and line spacing
Cross-checking accuracy of the contents page with chapter headings and page numbers
Detailed check for consistency within capitalisation, spellings (e.g. –se or –ze endings), abbreviations, hyphenation, font, layout, heading style, captions, formatting, presentation of dates and numbers, etc.