Thank you, that is what i was looking for.
PDFClown is a 3rd party tool that Kentico uses, so it's not really run by Kentico.
However, try adding this to the top of your code:
That should properly set the namespaces for your code snippet so it knows to use the pdfcloud namespaces for File, Document, and PrimitiveComposer. If that doesn't resolve the issue, then i'll need to know what error it's throwing.