If you save the documents as templates and create new documents from them, as intended, the issue of overwriting the template shouldn't arise so there is no need to make them read only.

If you are using content controls, add editors to the controls and protect the templates as read only and then you will only be able to type in the controls. Insert Content Control Add-In will do that for all the controls in a single operation.

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Graham Mayor - MS MVP (Word) (2002-2019)
Visit my web site for more programming tips and ready made processes www.gmayor.com