Need more context to understand what this is about - can't you check with your client?

I am guessing that this is a bag for delivery of medication that must be signed for or perhaps logged or registered in some way. This would in that case often apply to expensive items and items scheduled as drugs of addiction - narkotika/kontrolläkemedel.

It could also mean a bag that is sent sealed and should be signed for to garuantee that it was still sealed and had not tampered with up to the time of delivery.