So, journal files are apparently not encrypted/specific to the edge that created them.

I took a compressed journal file renamed it (jrnl_test.esj) , uncompressed it (to jrnl_test2.esj) , and moved the two files back to the edge in my generic Documents directory on the sdcard.
The Storage browser shows the uncompressed and compressed copies both as journal files.
It would not open either file directly, instead prompting to add them to the Library first.
After adding both files to the library, and going to the Library view in the Storage file browser I located them in the Journals section.
The Library/Journal app opens both files just fine.

So, to salvage a journal file
1) uncompressing the journals isn't necessary.
2) Rename the files to something meaningful. They only have to end in .esj


So, as far as I can see, most of the stuff in the backup file should be salvageable. Purchased books will have DRM applied, so you'll need the appropriate pin/user/password that Adobe expects to open the book on another device.

PDF files with annotation would be harder. There's the pdf file, then there's the annotation file, and a database that relates the two. Making that work together would require duplicating what the Library does to relate them in the database.

It looks like the annotations themselves are stored in the .esa directory under the library's .esi-content directory and named: *.esa and they contents are also compressed journal files.