It might not be the answer your looking for but it depends what you define as 'safe'?
V11 to 11.20 are reasonably close versions so there shouldn't be any major problems upgrading, but you should always make a backup of your CAL / licence allocations and reload schedules just incase, also a backup of the server would be a good idea.
You can also review the release notes for the version of 11.2 you are planning to upgrade to, incase you see anything that might effect your documents.
It also depends if this server is a live production server or a dev server, and if you can have the server down for longer than you expect if anything went wrong.
Maybe even request a trial licence from Qlik to mirror your current server, and install a 'test' server with the new version to make sure all your documents function as you'd expect.
Hi,I believe you can processed with the below steps
1.Read release manual 11.2
2.Take snap shot back of ur server
3. Else step2, Take back up of ur QV app doucmnets
4. stop the services of current server
5.execute 11.2 exe file
6.check ur server license
7.check ur app access.
hopes it helps,11.0 to 11.2 there is no major architecture changes.