From archaeological field work to heritage organisations and museums, increasingly CAD files and three-dimensional CAD models comprise a unique component of our digital archives - and one which it may not be possible to reproduce on paper. This Guide offers a basic description of computer-aided drafting or computer-aided design (CAD) software, discussions on the use of CAD in a variety of situations, descriptions of data acquisition methods including field survey and direct object scanning, and good practices in the use of the software. As well as providing a source of useful generic information, the guide emphasises the processes of long-term preservation, archiving, and effective data re-use. An important aim of the Guide is to introduce practitioners to areas and issues for which applicable standards and frameworks already exist and to identify the relevant sources of information that may be consulted.