As a proofreader, I can either read ‘blind’ – i.e. not against previous copy – or read against previous copy. And I can work either on hard copy or electronically (on PDF or Word). In Word, I tend to use the ‘Tracked Changes’ and ‘Comment’ features to indicate my comments and suggested changes. For PDF documents, I normally use Adobe DC’s Comments function to embed suggested insertions, deletions and replacements into the PDF. I can use current British Standard proof-correction symbols and terms, or use your own system.
In either case I would, among other things, identify and correct errors of grammar, punctuation and spelling that may have slipped through during the editorial stages; identify typographical errors introduced at layout; ensure that the page sequence within your document is complete and that illustrations are present or appropriate space has been allowed; and follow the editorial style guide (the list of spellings, etc. adopted by the copy-editor and passed on to the proofreader) if provided.
I would not seek to amend or ‘improve’ a copy-editor’s work unless specifically asked to do so by you.
I would, of course, correct or query any errors and omissions. I would also identify internal textual, typographical and design inconsistencies, and query or correct as appropriate; check that type size, style and fonts all appear consistent; and check bad word breaks and column breaks, and eliminate widows and orphans if required by you.
For a fuller description of what you can expect me to do when proofreading your text, please consult section 5.6 of the Society for Editors and Proofreaders’ code of practice.
Please contact me to discuss your project.