Unfortunately the table-header-group was ignored so we are not able to automatically handle page-breaks with any degree of sophistication.
We did however implement the <PB> tag so whenever this is found within the item description we will apply a page-break at the next row and translate across the table head section onto the new page.
This will at least allow you to have neat page-breaks and perhaps in future we will look at utilising a different PDF rendering engine that will support paged media properties.