This is tricky and I thought I could give you a better answer but I'm giving up. But I will share with you how far I got.
First your Japanese PDF has to be run through an optical character recognition with a Japanese character recognizer to create an overlay of the actual Japanese characters. I have done this for you. If you open this file, you will now be able to "select" text which you cannot do with the original file.
You should be able "in theory" to drop this into Google translate but that didn't work for me. Smallpdf.com did work but it wasn't translating all of the text and also wasn't including the images.
I suspect that one of the paid PDF translators will do it. Dunno. Maybe you can find a better service?