You can add comments to text, objects, charts, and table cells. When you don’t want comments to be visible, you can hide them. Comments are indicated with a square marker in the left margin of the document (text is also highlighted), next to an object, and by a triangle in the corner of a table cell.
When multiple people are working on a document, each person’s comments appear in a unique color and include their author name. Anyone can reply to a comment, which is especially useful if you’re collaborating—you can add a comment, then with back-and-forth replies have a conversation in real time.
Note: Comments and highlights aren’t visible in printed documents.
You can edit and delete your own comments and replies. If you’re the owner of the document, you can delete anyone’s comments, replies, or conversations.
Select text, an object, or a table cell, tap 
, then tap Comment.
Type your comment, tap Done, then swipe down on the handle at the top of the comment to close it.
To view, edit, or delete your comment, do one of the following:
Open a comment: Tap the comment marker.
Edit a comment: If you’re the comment’s author, tap the comment marker, tap in the text, type your changes, then tap Done.
If there are replies to your comment, you can’t edit the original comment by tapping its text. Instead, tap 
at the top of the comment. Tap Edit Comment, make your changes, then tap Done.
Delete a comment: If you’re the comment’s author or the document owner, tap the comment marker, then tap Delete in the comment. If there are replies to the comment, this deletes the entire conversation.
To close the comment, swipe down on the handle above the comment.
Tap the comment marker.
Do any of the following:
Review a comment or conversation: Swipe up to expand the view, then scroll through the text. If a comment is truncated, tap Show More. To quickly return to the top of the comment, tap the top of the iPhone screen. To reduce the size of the comment view, tap the handle above the comment.
Go to the next or previous comment (or highlight): Tap the arrows at the bottom of a comment.
View detailed information about the date and time the comment or reply was added: Tap next to the comment or reply. Only the author of the comment or reply and the document owner can see this information.
To close the comment, swipe down on the handle above the comment.
Anyone you share the document with—by sending them a copy or inviting others to collaborate (with editing privileges)—can reply to a comment.
Tap the comment marker.
Do any of the following:
Add a reply: Tap Reply at the bottom of the comment, type your reply, then tap Done. You can reply as many times as you like.
Edit your reply: Tap next to the reply you want to edit. Tap Edit Reply, make your changes, then tap Done.
Delete your reply: If you’re the reply author or the document owner, tap next to the reply, then tap Delete Reply.
To close the comment, swipe down on the handle above the comment.
If you’re the owner of the document or author of the original comment in a conversation (a comment with one or more replies), you can delete the entire conversation.
Tap the comment marker, then tap Delete at the bottom of the conversation.
Tap 
in the toolbar, then turn Comments on or off.