PDB can refer to many ebook formats, see the
Wiki. If these are TealDoc files, I'm not sure if any EInk device will read them.
The iLiad does have a standard Linux filesystem which is visible to the user, but it only presents six files per page in its file view.
Infovore: I agree that the Hanlin V3, and the
lBook, now support many drm-free ebook formats, but how is its ebook library arranged?