As frustrating as it is to spend money on a copy of the manual (which should be available online...), it's not too terrible - you get a good product. Jukeboxes are complicated mechanisms - much more complicated than a pinball machine or a video game, and have many more layers of parts. The manuals have it all laid out, and the copies available for purchase are *very* nice. Clean, easy to read, very clear pictures. I bought a reprint for my Rock-Ola on eBay because I needed it, and it was worth it. It's not just a crappy photocopy - it is a very good quality copy, crystal clear, comb bound, complete with the fold out pages of diagrams and schematics.
I can understand why juke manuals are available like this - they're much more in-depth than the manual for a pin or a video game. A PDF of one of these would be really hard to work from - and even harder to create in sufficient quality.
It would be really great if they were online - but I can't even begin to imagine how much time and effort would be required to scan them all. Not to mention how hard it would be to work from a mechanical diagram split across two pages since the fold-out won't fit in a scanner, or even the file size required to make everything legible.
That, and I do believe that someone still owns the copyright on these things.
-Ian