Thank you all for your responses.
My Paperwhite came with firmware version 5.6.1.0.2 already installed, so I guess jailbreaking it isn't going to be an option. Doesn't seem quite as necessary as it was (to me) with my old Kindle, so hopefully I will not find any compelling reason to jailbreak it, since I won't be able to do so, lol.
I wasn't having a problem with simply installing a dictionary; the installation into the documents folder was successful and I can access the book/s. What I wanted to be able to do was to put a different dictionary in the Dictionary folder (yes, there is a separate folder for Dictionaries on the Paperwhite, susan-cassidy; the Paperwhite comes with it already installed and already populated with the dictionaries of Amazon's choice.
) so I would be able to access the dictionary - or word usage book - of my choice via the dictionary/Wikipedia look up function of the Paperwhite.
Sadly, from what I am reading and from what I have experienced when trying to do so, the end-user has no control over what goes into the Dictionary Folder so only the dictionaries that came "built in" with the PW will work this way - unless you know of a made for Kindle dictionary that can be added, Doitsu??
It would be a very cool feature if you could add things to this "look up" function, like a Thesaurus, or a book of grammar or something like that. Sure, you can separately access any of these things if you have them on your Kindle, but having them added to the look up feature would be quite convenient!
As for the "feature" of other non-English dictionaries being added by the latest firmware, I was actually annoyed to see 30 unsolicited (by me) 'foreign language' dictionaries in my Cloud storage. Seems as if this uses up a lot of room for books that I will almost never access, and none of them can be deleted to make room for other things. Not that I am running out of room, but it's the principal of the thing, too! It would be a nice change if Amazon would allow the end-user complete control over what books are on their device and in their supposedly 'personal' Cloud storage.
Holly