I have large tree, with many `pdf` files in it. I want to delete the `pdf` files in this tree, but only those `pdf` files in sub folders named `rules/` There are other type of files inside `rules/`. The `rules/` subfolders have no other subfolders.

For example, I have this tree. Everything below 'source'

 source/
 A/
 rules/*.pdf, *.txt, *.c,etc..
 etc/
 B/
 keep_this.pdf 
 rules/*.pdf
 whatever/
 C/ 
 D/
 rules/*.pdf
 something/

and so on. There are `pdf` files all over the place, but I only want to delete all the `pdf` files which are in folders called `rules/` and no other place.

I think I need to use

 cd source
 find / -type d -name "rules" -print0 | xargs -0 <<<rm *.pdf?? now what?>>>

But I am not sure what to do after getting list of all subfolders named `rules/`

Any help is appreciated.

On Linux mint.