PAB aka Personal Address Book is the address book file associated with Microsoft email clients such as Microsoft Outlook or Microsoft Exchange Server application. It contains information for personal and organizational contacts. The PAB file stores address book separately from the email data. It can be added to account user's email profile and the contacts can be added manually.
The PAB file can be found at the following locations. The default location of PAB file depends of the version of OS installed in the user machine. For each version, the default location will be different: