https://help.cbp.gov/app/answers/detail/a_id/1380/~/trusted-traveler-program---what-do-i-need-to-bring-to-my-interview%3F (mirror) says:
The following original documents are usually required:
[…] Documents providing evidence of residency. Examples are: driver's license (if the address is current), mortgage statement, rental payment statement, utility bill, etc. This is not required for minors.
Does one have to bring a physical document for the proof of residency for the global entry interview, or is it ok to show an electronic version of it (e.g., on a laptop or tablet)?