Contractors often rotate between sites and operators, and asking every one of them to install and log into another app slows down the start of every job. The simplest option is usually a web link that opens the permit or the relevant part of it in a browser, with the contractor’s identity confirmed some other way, like a code or a supervisor’s confirmation.
The tradeoff is that browser access usually needs a connection, so for offline sites the contractor may still need the app or need to work through the site’s own crew. Either way, the permit record should show clearly who the contractor was, what they signed and when.