The reader is just an Android View (PDFLayoutView or PDFGLLayoutView).
You can include the view to the fragment (programmatically or by xml definition, it can be its root view if you want to), and implement ILayoutView.PDFLayoutListener to handle the callbacks and create a PDFViewController to manage the reader actions (check OpenTask in PDFGLViewAct or PDFViewAct).
More or less everything that's done in the activity can be moved to your fragment.
Do not forget to handle the onDestroy action to release SDK resources