Desktop Printing Software is included with System 7.5 Update 2.0, it is in TOME 7, however you must use the Custom Install feature to install it. Within the "Custom Install" area of the Installer, expand the "Printing SW Updates" item and click the "Desktop Printer 1.0.3" box. This installs all of the necessary resources for Desktop Printing. You will also need to enable Background Printing in the Chooser.
There are a couple of other ways to obtain the latest version of Desktop Printing software using specific printer installers such as Color LaserWriter 12/600 8.3.2 installer, Color StyleWriter 2500 installer, or Color StyleWriter 1500 installer.
The standalone Desktop Printing SW 1.0.3 installer ReadMe states a need for an earlier version of desktop printing software because of these other component requirements; Finder v7.1.4, Clipping Extension, Networking Extension, Thread Manager, Drag & Drop extension, and the Dragging Enabler.