It seems the General Knowledge Base and its successor program GeneralKB possess the capability of PDF export and a such it should be easy enough to convert KBD to PDF. Also some dedicated PDF exporters may support *.kdb files.
Convert General Knowledge Base document file to Adobe Portable document format.
We found 2 software records in the database related to .kbd to .pdf file format conversion.
Microsoft Windows software - convert kbd to pdf on Windows
Knowledge management software
Convert from kbd file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned kbd to pdf. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
On-line services software - convert kbd to pdf on web
A web-based document to PDF converter