As the amount of product iterations within high variety low volume assembly environments increases, the need for efficient management of variability and engineering changes within assembly instructions rises. This work proposes a methodology and a system architecture that facilitates the interplay between product lifecycle management (PLM) systems and digital assembly instructions, using an ISA-95 based data model. The framework consists of three main components: (1) a product variability model that integrates PLM information, (2) a digital instructions authoring tool, and (3) an assembly instruction variability model that connects to instruction platforms. Finally, the approach is applied to a validation case.