The authors or reviewers add annotation as:

🧠 Explanation:

Authors or reviewers add annotations as comments. In documents, especially during editing or reviewing, comments are used to give feedback, suggest changes, or highlight important points without altering the main text. This feature is common in word processors like MS Word or Google Docs, where comments appear in the margin and can be replied to or resolved. Comments help maintain clarity between the original content and reviewers’ notes. In grammar, “comments” is a plural noun referring to these written remarks. Alternatives in context could be “notes,” “remarks,” or “feedback” depending on the reviewing platform.