Conversion of bak files to pdf file format

BAK files are generally just renamed backup copies of the original file, so if your file was PDF, you can simply rename it back and open using PDF Reader. If that's not the case, your .bak file is not PDF backup and there is most likely no way how to convert it.

You might also want to check out some file analyzer software to determine what kind of .bak file it is and whenever it may be even exported as PDF document.

Open BAK file    Open PDF file