You can disable RadEditor by setting RadEditor1.Enabled = False in the codebehind.
You can do that for example in the Page_Load event, in a button click or another handler, e.g.
Protected Sub form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles form1.Load
RadEditor1.Enabled = False
For your convenience I have attached a sample project.
All the best,
the Telerik team
Do you want to have your say when we set our development plans?
Do you want to know when a feature you care about is added or when a bug fixed?
Telerik Public Issue Tracking
system and vote to affect the priority of the items