How to disable restore/resume/saved-state for a specific application in Yosemite
After some playing around I found a workaround, not sure if there's something better:


Open Preview, close all documents, close Preview.
cd ~/Library/Containers/com.apple.Preview/Data/Library/Saved\ Application\ State/com.apple.Preview.savedState
chmod -w .
chmod -w *


There will be similar folders for other applications.