It might be possible that Nikon RAW images can be converted to Pentax RAW images in some of the professional digital photo editing program. Although RAWs are not commonly converted between each other.
Convert Nikon Digital SLR camera RAW image to Pentax Digital Camera Raw Image Format.
We found 10 software records in the database related to .nef to .pef file format conversion.
Microsoft Windows software - convert nef to pef on Windows
Adobe's professional tools for RAW image management and post-production
Convert from nef 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 nef to pef. 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.
Program used to manage pictures and photos
Fast and inexpensive app for creating impressive landscape images
A professional photo editor and manager for Windows
One of the best bitmap graphic editing program
A complete image retouching program
Photo Manager is digital photo editor and manager for Windows
Apple macOS / Mac OS X software - convert nef to pef on OS X
Mac version of Adobe' professional digital photo editing tools
Mac version of popular digital image editor
Linux/Unix software - convert nef to pef on Linux
A digital photo editing and converting software for Linux