This chapter explores the implications for UK trade mark law arising from the use of a computer-aided design (CAD) file. The possibility for a CAD file to be edited and uploaded onto an online platform ready for 3D printing means that a trade mark could easily be attached to or detached from a CAD file, which could then be sold and disseminated on the Internet. This not only facilitates trade mark infringement, but can potentially impair the function of a trade mark, its origin and the quality guarantee. However, an analysis of current trade mark law in the UK does not clearly indicate whether the above-mentioned digital activities directly constitute trade mark infringement. For this reason, the authors of this chapter present an in-depth analysis of UK trade mark law in order to shed light on the various issues arising from CAD creation and modification for 3D printing.