After you set up the Check In/Check Out system, you can check in and check out files on a remote server using the Files panel or from the Document window.
If you check out a file, then decide not to edit it (or decide to discard the changes you made), you can undo the check-out operation and the file returns to its original state.
To undo a file check-out, do one of the following:
Open the file in the Document window, then select Site > Undo Check Out.
In the Files panel (Window > Files), right-click (Windows) or Control‑click (Macintosh), then select Undo Check Out.
The local copy of the file becomes read-only, and any changes you’ve made to it are lost.