How to Lock a ParagraphUnitSegmentPair inside of a Batch task

I'm using the Batch Task API to create a Segment locker task. Essentially, depending on some context info, the task decides whether to lock a segment pair. So far, everything I've tried to do to lock a segment Pair doesn't show up when I open the file for editing. 

I add a new BilingualContentHandlerAdapter

While inside the ProcessParagraphUnit of the SegmentLockerPreProcessor I've tried several approaches:

And also with editorController, but in that case, the activeDocument is null

Can this be done inside ProcessParagraphUnit? And how?