I register my DW, and 2/3 of the time, when I send her the email to sign the waiver, it falls into the netherverse. If that happens, we just wait until we get to the expo. Right before the bib pick up exhibit hall, there will be a table or two with paper waivers. Just have your bib number(s) handy, as they will be needed for each waiver. When you go pick up your bibs, just hand over the paperwork, and they'll take care of the rest.