Note: If you don’t want to associate another email address with your Apple Account, you could instead ask the owner of the shared document to invite you again using an email address or phone number that’s already associated with your Apple Account.
Go to the Pages app Accept an invitation to collaborate.
Edit the document.
Edits you and others make to the document appear in real time. Cursors and selections of text and objects appear in different colors to indicate where others are currently editing. Move your pointer over a cursor to see who’s making the edit.
In a shared document, click Collaborate on documents in Pages, Numbers, and Keynote.