Unidrv.hlp is the Windows Help file for the Universal Printer Driver (Unidrv) , a core component of the Windows printing subsystem from Windows 95 through Windows 7 (and present, though less visible, in later versions). A "Unidrv Download Printer Driver" typically refers to a custom printer driver built using Unidrv's minidriver framework, which relies on a text-based GPD (Generic Printer Description) file and associated resources.
Instead, identify your printer model and get its official driver from the manufacturer. If you are a developer studying legacy driver architecture, use the Microsoft Windows Driver Kit (WDK) samples or the archived Windows Hardware Dev Center. Unidrv.hlp Download Printer Driver