Make read-only documents in TextEdit on Mac
In TextEdit, you can make a document read-only so it can’t be edited, or lock it so it can’t be edited or deleted.
If you own a read-only or locked document, you can edit it after removing its read-only state or unlocking it. Others can only edit a copy of the document.
In the TextEdit app on your Mac, do any of the following:
Make a document read-only: Choose Format > Prevent Editing.
To allow editing, choose Format > Allow Editing.
Lock a document: Place the pointer to the right of the document title at the top of the document window, click the arrow that appears, then select Locked.
To unlock a document, deselect Locked.