This file is a .pdn Paint.Net file.

If you changed some binds in the config file you can make a new image with that file quickly by adjusting the "layers".

A special format that Paint.Net uses that is similar to Photoshop.

https://www.getpaint.net/

About it...
"Paint.NET is image and photo editing software for PCs that run Windows. 
It features an intuitive and innovative user interface with support for layers, unlimited undo, special effects, and a wide variety of useful and powerful tools."