RoboHelp 8 ushered in an ability to link a Word document to RoboHelp so that ongoing maintenance may occur in Word. In the RoboHelp Project Manager pod the icon will reflect the status. For example, if the Word document is updated, the icon changes to alert the RoboHelp author their HTML copy is different. They then right-click and update the Word to suck into RoboHelp the changed content.
Keep in mind that I'm only aware of this. I've played with it on a fundamental level. I'm not sure what happens if you have links that you construct from the Word content that exists as HTML in RoboHelp. They may get wiped out during an update.
Also, it behooves anyone using this approach to be rather diligent in use of applying Headings and other formatting properly in Word.
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In TechComm Suite 3, there seemed to be some collaboration component of Framemaker that looked...possible, but too complex for a simple need. What you describe sounds much more workable.
Will grab the RoboDemo trial when we next have the chance to check into this. Keeping the edits to Word would be easiest for the various document folks. It'll be interesting to see how...smoothly the publish and sync process is.