How to Unlock Selection in Word

If you have Office 2013, you don't have a subscription version; that would be Office 365. But the two most common causes of the "selection is locked" message are (1) an unactivated version of Office and (2) a document that is protected in some way, usually for forms using legacy form fields.

How do you" unlock the selection" when in Word document

Try this:-

Click in the field that’s locked; this should cause it to be highlighted (in grey on my pc) then:-

Crtl+SHIFT+F11

The above command should perform the unlock.

(You can check this by hitting the F9 key to update the (now unlocked) field.

ALTERNATIVE TO THE ABOVE (DEPENDING ON YOUR MACHINE)  

Ctrl+SHIFT+FN+F11

My ref 84 a and b.

How do you" unlock the selection" when in Word document

If you’re talking about Master and Sub Documents see here:-

https://www.techwalla.com/articles/how-to-unlock-word-documents  

 - section called:-

Unlocking Subdocuments