User-agent: * 
Disallow: /Tijdschrift/
Disallow: .pdf$
Disallow: /.pdf$
Disallow: /*/.pdf$
Disallow: /*/*/.pdf$
Disallow: /*/*/*/.pdf$

Disallow: /*/*/*/*/.pdf$
Disallow: /*/*/*/*/*/.pdf$
Disallow: /*/*/*/*/*/*/.pdf$
Disallow: /*/*/*/*/*/*/*/.pdf$