Additive Manufacturing is capable of producing highly complex and personalised products. However, innovation in both material science and processing is required to achieve the performance, reliability and miniaturization of modern mass-produced electronic systems. This article presents a new digital fabrication strategy that combines 3D printing of high-performance polymers (polyetherimide) with light-based selective metallisation of copper traces through chemical modification of the polymer surface, and computer-controlled assembly of functional devices and structures. Using this approach, precise and robust conductive circuitry is fabricated across flexible and conformal surfaces omitting the need to connect and assemble separate circuits. To show how this process is compatible with existing electronic packaging techniques a range of modern components are solder surface mount assembled to selectively metalized bond pads. To highlight the potential applications stemming from this new capability, high frequency wireless communications, inductive powering and positional sensing demonstrators are manufactured and characterised. Furthermore, the incorporation of actuation is achieved through selective heating of shape memory alloys with a view towards routes towards folding and deployable 3D electronic systems. The results in this paper show how this process provides the required mechanical, electrical, thermal and electromagnetic properties for future real-world applications in the field of robotics, medicine, and wearable technologies.