Additional Reference: PubNub Github Repo README Instructions
Important Notes
Make sure that your iOS project (.xcodeproj) is within a Xcode Workspace (.xcworkspace). Being in a workspace rather than a project changes Xcode behavior when drag-dropping files.
If you are only in an .xcodeproj, then it doesn't prompt you with options to "copy items if needed" and automatically creates symlink rather than copy files into project (hence being susceptible to the changes in the original PubNub project).