Preview is not now, and have never been AppleScript-able, which does suck. It'd be nice if it were, though.
From this blog:
However, from 10.4–10.6 it was possible to enable the default Cocoa
scripting support via these Terminal commands:
sudo defaults write /Applications/Preview.app/Contents/Info
NSAppleScriptEnabled -bool YES
sudo chmod a+r /Applications/Preview.app/Contents/Info.plist
This was sufficient to
be able to get at the file of the current document to delete it,
change its Finder label, import it into EagleFiler, etc. Under 10.7,
modifying the Info.plist file breaks the application’s code signature.
I would expect this to cause a harmless warning message in the
Console, but it actually causes Preview to crash.