User documentation was inline with the code (think perldoc/pydoc). Developer documentation (as comments) was also co-located with the relevant code.

This automatically gave us man pages at a shell prompt. We could include those man page outputs in report .zip files that got emailed to users, and push them to our website.

There's an art to keeping this organized. Always having a good trail of breadcrumbs was important, like a comment next to a variable assignment telling the developer to update the user docs if that constant is changed. Also avoiding duplications, which leads to drift/inaccuracy. We considered inaccurate documentation to be a bug. Full time employees took to this. Contractors often needed reminding.

As the project grew there was managerial pressures to get involved in other stuff like power points and sharepoint.