I have a Kindle Paperwhite, 2012 version, and I have downloaded books and documents to it from the built-in experimental browser, not from Amazon, but they does not show up on other devices connected to my Amazon user. Does anyone know how to transfer them to those other devices? Preferably without installing a lot of other programs and stuff.
If you didn't purchase the books from Amazon, they won't be synched to other devices, because (among other reasons) Amazon doesn't know they're there. There's no upstream sync mechanism.
I don't have a paperwhite, but I have a K2, DX, Fire HD, and Android reader.
The sync mechanism for non-Amazon content without installing anything anywhere involves a computer and 2 USB cables.
Plug both devices in, open them each in a file browser window, find the right folders, and drag across.