Technology has certainly come a long way and it’s relatively easy to check in to hotels using documents saved on mobiles phones, perhaps in email form, but that’s not always the case at airports.
Some airports may permit E-documents but they will often state that these need to be printed, and they cannot simply be passed over on a mobile phone. Hotels in some European countries will want exactly the same, so while the world is a whole lot more technological, there’s still a need to have things printed out crystal clear, especially in high security airports.
If you’re unsure on whether your E-documents should be printed, then it’s better to print them just in case. Occasionally these documents require details written out on your behalf so read it through thoroughly and you’ll be a lot less likely to run into any issues in the check-in.