Corrections should be made using PDF annotation tools (like Adobe Acrobat Reader) or through the publisher's web interface.
A refers to accessing this finalized PDF or digital file, usually through a secure online production portal, to review it for corrections. The Importance of the Proofing Stage proof download
A "proof" (or page proof) is the preliminary version of a publication, such as an article, book chapter, or design layout, that is produced after typesetting. It shows exactly how the final content will look—including layout, formatting, images, and text positioning—before it goes to press or is published online. Corrections should be made using PDF annotation tools