Hi,
actual Swift module is released for free and in opensource: our aim is to let users have full power on them.
In RadaeeSwift folder you can find the Obj-C project to build the libRDPDFLibSDK.a used in Swift demo project.
You are free to modify or add code to customize the SDK; in this case, you can add a method to RadaeePDFPluginDelegate to get the clicked url from OnAnnotOpenURL.
We're also developing a more powerful module, it will be released under subscription. The subscription will allow you to ask for some custom development.
If you're interested on such opportunity I invite you to open a ticket and address it to sales department: you'll receive more details about that.