PDB is a general container format and can hold a lot of different formats. The
JetBook Lite supports the
EReader PDB format. These often have DRM.
Calibre can convert non-DRM EReader (as well as other) format PDB files. As abookreader you would have to remove the DRM first (if required) but after that calibre can convert it to MOBI for reading on a Kindle. calibre will also tell you if the book has DRM or not.