(?i)!*.Pdf do the job but when you try to exclude all rest with a star *, it cuts the subdirectories too. So you only have the root .pdf.
(Spending 2 days with this…)
So the target was to design generic subfolder content with something like
**/*.pdf, **/**/*.pdf,
but I didn’t succeed. So I had to list all directories in the exclude file.
Inspired from : (searching source). Edit : found un-ignore subfolders & files of ignored folder