Nexus 10 - error copying file - not supported

[suxen01]

Hi
i got error file not supported when copying file from Pc to tablet via Usb cable
what i have to do is before
change extension of file(tryed w/ pdf, epub) to jpg
than copy success,
from tablet folder, change again extension to original

there s some setting missing in my tablet....as for windows file / app association ??

thanks
I tryed to search for similar topics..no results