And maybe if you want to test if it's really about the UTF-8, you could convert the readme to ISO and try to print that...

For example like this:
ConvertText sys:Applications/VectorInk/ReadMe ram:readmeiso SE=UTF-8 DE=ISO-8859-1

And then:
copy ram:readmeiso netpar:

BTW. for my printer there was two PPD files available, one for ISO-8859-1 and one for UTF-8.... if that would affect... I haven't tested changing them though...