It's difficult to make much in the way of a suggestion without seeing the design of your layout.
Two general observations:
it can be difficult to control page breaks the way we'd like in Filemaker.
A list view report based on your portal table that groups those records with a subsummary part is more flexible than printing on a layout where you used your portal to view and edit this data.
In general it is worth considering that portals are designed for screen display, not printing. It makes better sense to build a report on the most granular table in the report (perhaps your sub-sub-topic table?) and use the list layout options available to construct the report.
On the other hand, if you feel you use use a portal (and it may be the best way in some circumstances, perhaps a large portal that displays a single record) then you must regard the portal itself as a single object, just as you would an image, say, and design that object so that it fits within a single page's printable area.
It makes better sense to build a report on the most granular table in the report (perhaps your sub-sub-topic table?).
Level of granularity is an important criterion when choosing a report layout - so important that it bears constant repetition.
Thanks guys - completely makes sense