Lifehack: you can annotate a PDF with a signature and just send it to the receiver.
The only time I couldn't do that was when I needed a notarized document.
> Regarding travelling, is no fun when something happens trying to show the ticket from an app that for whatever reason decides not to start, or having the phone dying on me. Paper to the rescue.
Yup. I save screenshots of barcodes for tickets and other stuff instead. I have a second phone as a backup :)