> I wonder what happens if they lose your money due to bugs or even intentionally - will they then happily accuse you of forging the PDFs because they're unsigned?

> With paper that'd be not so trivial, in my country the paper often has some special format and the paper itself is of a special type, and it ages and you cannot easily guess the printer which was used.

Read a similar discussion recently. Even with paper you can prove your account balance at day X but if your bank lose your money at day X + n and you want it back they could still claim you withdraw all since day X and had an empty account at day of lose.