How do I switch to View-only mode while reading my notes so I don’t accidentally make any changes?

Android 

To switch to View-only mode to lock your notes so they can’t be edited, bring up the overflow menu (three dots in the upper right corner or menu key on some devices). Then choose View-only

To switch out of View-only mode to be able to edit the note, bring up the overflow menu again, and choose Edit, or simply tap the Edit button in the lower left corner.

Windows/Windows Phone

To switch to View-only mode to lock your notes so they can’t be edited, first bring up the app bar menu by swiping from the bottom of the screen (Windows) or by tapping the three dots in the lower right corner (Windows Phone), then choose View only.

To switch out of View-only mode to be able to edit notes, bring up the app bar menu again, and choose Edit.

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