No clue. I'll tinker.
Edit: No, I'm just getting increasingly bizarre errors. Perhaps David will check in and shed some light on this one.
For the moment, it's back to my brute force method, which does work.
AlbumSynchronizer AlSy = new AlbumSynchronizer(engine);
It works for PDF but still gets an error about registering variables on template pages. I will have a another look.
Move the new AlbumSynchronizer call outside the iterator for performance (i.e before it)
Move the ao.setChildren(ao.getChildren()); call outside the iterator too (i.e. after it) for performance reasons, otherwise you will write to disk for each album object instead of doing one write per folder.