The Read-Only Document action is located on the Document sub-menu of the File Menu.

The Read Only Document action is a toggle that switches the current document's file attributes between Read-Only and Read-Write. If set to Read-Only, you can no longer edit that document until you toggle the document to Read-Write using the Read Only Document action. This condition persists across different sessions of the program. Closing and relaunching the program does not change this setting.

Setting the document as Read-Only also turns off spellchecker text highlighting for that document only.

The Read Only Document action should not be confused with the Read-Only Note action, which prevents editing of a note from the program's main window.

Visual Indicator: When a document is set to read-only, the background color of the Note Title Bar is changed to a configurable color, red by default. This color can be changed on the Display Settings page of the General Settings dialog.