<p>Industry 4.0 (I4.0), the fourth industrial revolution, includes digital manufacturing as one of its main elements for enhancing production procedures. In the context of I4.0, digital manufacturing uses real-time data from electronic sensors, actuators, and other connected devices to help manufacturers improve their production processes. I4.0 relies heavily on internet-based digital manufacturing platforms, allowing producers to design, evaluate, and improve their practices efficiently and cooperatively. Manufacturing processes could become more efficient, reliable, and flexible with digital manufacturing, as this could lead to quicker production cycles, higher-quality goods, and more affordable costs. This review provides a critical examination of the adoption of prominent technologies related to I4.0, with a specific focus on the technologies having technical enablers, industrial applications, and barriers to implementation. The literature review demonstrates a growing integration of IIoT, edge computing, and AI to support real-time decision-making, along with persistent challenges that continue to limit adoption, such as a lack of interoperability, data governance, and standards. The review highlights some of the current trends in multi-material and large-scale additive manufacturing technologies, AI-enhanced cybersecurity, and digital-twin-driven process optimisation. By consolidating research in various domains and focusing on ongoing challenges, this review provides a systematic pathway to developing secure, interoperable, and sustainable digital manufacturing in the era of I4.0.</p>