INDD is a control file used by Adobe InDesign software. It allows multiple user to work on the same project without changing the underlying INDD source document. While editing, a hidden IDLK file is created in the users computer that prevents changes made by other users of the editing group.

Group work option available in Adobe software facilites teamwork between content creators (InCopy tool) and graphical designers (InDesign tool). The function that generates IDLK files in Adobe InDesing is called ‘check out’.