In Mac OS, you can lock a file in order to make it read-only and prevent it from being accidentally deleted.
Note: If your document is shared, anyone who has Write privileges can clear the read-only status. For stronger protection, require a password to save changes.
Open the Finder and select the document you want to protect.
On the Action pop-up menu , click Get Info.
Note: You must be the owner of the file, or have Write privileges, in order to clear read-only status.
Open the Finder and select the document you no longer want to be read-only.