(everything except the iPad which doesn’t let me get the file for some reason, at least as far as I can see)

What I've discovered is that if I email a doc, or PDF, to my Kindle account, Amazon sends out a confirmation email.  If I click on the embedded AZW link in Safari (on the iPad), it will then attempt to download the file and I get a subsequent prompt to open it in my iPad Kindle app.  And once it's opened, it remains part of the "library" on my iPad.