Offline access is allowed on a computer-by-computer basis. In other words, you must allow offline access for each individual computer where you'd like to view your documents and spreadsheets without an Internet connection. Offline copies of your documents and spreadsheets will be synced to each computer where you've enabled Google Slides offline.
Anyone with access to a computer with offline access enabled will be able to view all of your synced documents and spreadsheets when they open Chrome. To help protect the security of your data, we strongly advise that you don't allow offline access on public or shared computers. Instead, allow offline access on personal computers where only you have access, and where your access to the computer is password protected.