Saudi Arabia is pursuing pharmaceutical localization, industrial diversification, health security, and digital transformation under Vision 2030. Yet local manufacturing capacity alone does not guarantee reliable medicine supply. Pharmaceutical plants must convert volatile demand, imported-material constraints, validated process capacity, quality-release requirements, and regulatory obligations into executable production plans. Enterprise resource planning (ERP) systems can provide the digital backbone for this task, but value depends on integration with manufacturing execution, quality, laboratory, warehouse, maintenance, supplier, and advanced planning systems. This integrative review examines how ERP-enabled digital transformation can strengthen pharmaceutical production planning in Saudi Arabia. Recent pharmaceutical and Industry 4.0 literature is synthesized with Saudi policy and regulatory sources to identify planning capabilities, integration requirements, governance risks, and implementation priorities. The review argues that ERP should be treated not as an administrative transaction platform but as the controlled planning layer connecting demand, master production scheduling, material requirements planning, finite capacity, procurement, inventory, manufacturing execution, and batch release. A six-domain framework is proposed covering master-data integrity, integrated planning, execution visibility, quality-by-design information flows, analytics, and governance. The paper also presents an architecture for ERP-MES-QMS-LIMS-WMS-APS integration, a balanced KPI framework, and a phased 2026–2030 roadmap. For Saudi pharmaceutical manufacturers, the expected strategic value is improved schedule reliability, material readiness, capacity utilization, traceability, technology-transfer readiness, and resilience. The central conclusion is that digital transformation of planning should be built around validated processes, standardized data, cross-functional governance, and progressive integration rather than isolated technology deployment.