I keep 300dpi colour scans of current and expired passports, national IDs, etc. of me and my family. Stored locally on my home computer and synced to my MEGA Account. In Thailand I can't remember an instance where the digital copy was accepted in lieu of the physical copy. However, in theory one could obtain a printout and sign it in cases where a signed copy of a doc is required, the original is not required and not to hand. Once, when leaving Switzerland to fly to somewhere in The Schengen Area, Border Control demanded my UK passport in addition to my Swiss Ausweis before letting me go to the gate. I was confused by this as it had never been necessary in the past and I hadn't packed it. The chap in the booth reminded me that the UK had recently left the EU & EEA. I said "We're <deleted>!" and offered the high-res scan stored on MEGA. I am sure this should not have been enough, but the official accepted it and let me go through.