Proofreading is not editing, though a lot of people tend to confuse the two. Light copy editing is proofreading plus added expertise in ensuring style consistency appropriate to a publication or organisation.
Proofreading usually is the last and final check of a document or text prior to publication. This takes place after it has been edited to ensure the absence of errors. A proofreader will review text for spelling and punctuation errors, typos, or incorrect use of regional languages/dialects (i.e. Swiss German vs. High German).
While this can be done electronically, in publishing it is mostly done on a printed PDF-file, as it is important not to change anything in the finalised and already edited documents.
For an overview of the various editorial services, please click here: editorial services explained.
Please feel free to pass along a few paragraphs to word [at] elakremer.de to get them reviewed and see what kind of notes, comments, and changes I would make.