You can find a PDF version of "Kaas" online, but I must remind you that downloading copyrighted materials without permission might be against the law in your region. That being said, here are a few options:
Purchase the Granta Books edition of Cheese (ISBN: 978-1847082785). It comes with an introduction by renowned critic James Wood. While it is not a free PDF, the digital version you buy can be downloaded as a high-quality, searchable PDF immediately. That is the closest you will get to the "perfect" file. willem elsschot kaas pdf best