Comments: You can add comments to any part of a document by highlighting the relevant line of text. In the toolbar that pops up, click the speech bubble. Your comment will appear in the right margin. Add an @ mention to alert your colleague.
Attribution: Paper displays an author’s name next to any text they contributed—even if the text is copy and pasted from another Paper document.
Task lists: You an create lists of to-do items in any document by highlighting text and clicking the check-mark icon in the popup toolbar. Then put @ mentions next to each task to assign them.