"Link Sharing" allows a project owner to share their project via secret links. Anyone who has one of these secret links to a project will be able to view and/or edit the project, depending on the type of link used.
To turn on link sharing, click the "Share" button in the toolbar
Then click the "Turn on link sharing" button in the dialog
When link-sharing is turned on, you will see two secret links which can be shared with anyone you want to give access to.
Link sharing can be turned off from the same "Share" dialog as it is turned on. When turned off, the secret links will no longer allow access to the project.
When link sharing is turned on, the Review panel will show an option to enable track changes for Guests which are accessing the project via shared links. Users accessing the project using an edit link will have access to the Review pane and Track Changes. Anyone accessing the project using a read-only link will not be able to access the project's Review pane or view Tracked Changes. This includes access to any review comments in the project.