PDB file extensions were designed for Palm-based PDA devices. PDB file extensions lack the features of today's eBook. This file extension supports reflowable content for the older smaller palm and PDA devices. Low storage space on Palm devices requires the PDB file type. The PDB files make life a lot easier for owners of Palm-based and PDA devices.. File extensions of all types have enabled users to do a lot more work in far less time simply by being able to store it more effectively. There are file extensions for every data job out there. Everyday use of this type of file has continued to stay stable regardless of newer types of devices on the market today.PDB file extensions will always offer peace of mind to these Palm Pilot and PDA users. See below programs that can open PDB documents: ICE Book Reader, Palm Reader, Microsoft Visual Studio, Pegasus and Quicken.