It can be done in Word by using IncludeText fields.

I would also explore the option to create both versions in the same document and use a macro to show/hide content depending on which version you want to see. I've just done a template along those lines and I used Content Controls to tag areas and then used a macro to loop through the CCs and show/hide that content depending on the tag.

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Andrew Lockton
Chrysalis Design, Melbourne Australia