Mac OS X Preview pdf set password greyed out on Lion

[dancook99]

I scan my important docs like passport, DL, etc. and store them in my Dropbox. As an additional protection, I was setting a password on my pdf files using Preview with Snow Leopard.
Since I upgraded to Lion, the Preview menu - password is greyed out. Has this very useful feature gone with Lion ?

 

[dancook99]

Found a way but

Duplicate. This will create a copy of the original document. When exiting the copy, the Encrypt box can be checked and password entered.
Still, I have to trash the original and rename the copy to the original.