Hello there and thank you for posting on Expert PDF forum website.
Insufficient administrator privileges may also prevent you from activating Expert PDF successfully.
Please click using the right-hand-side mouse button on top of Expert PDF shortcut icon on the desktop and select option Run as Administrator. Using copy-paste method introduce the licence key you’ve paid for in order to activate the software. Make sure there aren’t empty interval spaces in front and at the end of the sequence.
Expert PDF Support team