Proof reading is the careful reading (and rereading) of a (yet to be finally-printed) document, to detect any errors in spelling, punctuation, or grammar. It may also involve checking of different elements of a layout (such as headlines, paragraphs, illustrations, and colors) for their correct dimensions, placement, type, etc.
Editing
the objectives of editing include (1) detection and removal of factual, grammatical, and typographical errors, (2) clarification of obscure passages, (3) elimination of parts not suitable for the targeted audience, and (4) proper sequencing to achieve a smooth, unbroken flow of narrative.