Then you can read some documentation and edit directly the Reference Pages (there you can define sub-page generation and such). Not very flexible editing rules, but somewhat acceptable (since you can catch up a bit with CSS).
This is one important thing that must do. In standard FrameMaker you can define external links by using Markers (e.g. via the Special->Hypertext or Special->Marker Windows). You mark some text with a special character tag and then enter "message URL ....." (read the doc please). Well this will not work in Frame+SGML ( unless there is some configuration, read/write etc. stuff to do I did not understand ). Again: bad bad documentation.
Anyhow, here is my solution just for HTML (nothing for PDF !) : In your DTD define a A Tag ( or do something with XLINK, have to think about this ). Then edit the Reference Page like this (provided you got a simple <a href=""></a> kind of element.
This solution is half-baked, because PDF will not have links ... Help me please !
Needs configuring plus CSS post editing. This is really important if you work for a business, because your HTML will really look ugly. I used standard Framemaker a lot to write slides for my teaching and it can be quite productive (see: http://tecfa.unige.ch/guides/tie/tie.html ) Note that the HTML CSS is NOT the same as the XML CSS, so do NOT put the files in the same directory ....