Hotkey to toggle custom file filter

I have a lot of PDF files. I would like to create a hotkey that would allow me to toggle a PDF file filter On & Off: 'Toggle on'-only PDF files, 'Toggle off'-all files.

This seems like it should be really easy but I couldn't find anything in the forum and I'm obviously not bright enough (or too lazy) to figure it out on my own.

This should be all you need:


It acts as a toggle automatically.

Outstanding! This was just what I was looking for.