Adobe Type Manager (ATM) is the name of a family of computer programs created and marketed by Adobe Systems for use with their Type 1 fonts. The current version is Adobe ATM Light 4.1.2, available from Adobe's FTP.
The original ATM was created for the Apple Macintosh computer platform to scale PostScript Type 1 fonts for the computer monitor, and for printing to non-PostScript printers. Mac Type 1 fonts come with screen fonts set to display at certain point sizes only. In Macintosh operating systems prior to Mac OS X, Type 1 fonts set at other sizes would appear jagged on the monitor. ATM allowed Type 1 fonts to appear smooth at any point size, and to print well to non-PostScript devices.
Around 1996, Adobe expanded ATM into a font-management program called ATM Deluxe; the original ATM was renamed ATM Light. ATM Deluxe performed the same font-smoothing function as ATM Light, but performed a variety of other functions: activation and deactivation of fonts; creating sets of fonts that could be activated or deactivated simultaneously; viewing and printing font samples; and scanning for duplicate fonts, font format conflicts, and PostScript fonts missing screen or printer files.
Around 2001, with Apple's Mac OS X (and Microsoft's Windows 2000 and XP), support for Type 1 fonts was built into the operating system using ATM Light code contributed by Adobe. ATM for Mac was then no longer necessary for font imaging or printing.
Adobe discontinued development of ATM Deluxe for Macintosh after Apple moved to Mac OS X. Adobe ceased selling ATM Deluxe in 2005. ATM Deluxe does not work reliably under OS X (even under Classic), however, ATM Light is still helpful to Type 1 font users under Classic.
Adobe ported these products to the Microsoft Windows operating system platform, where they managed font display by patching into Windows (3.0, 3.1, 95, 98, Me) at a very low level. The design of Windows NT made this kind of patching unviable, and Microsoft initially responded by allowing Type 1 fonts to be converted to TrueType on install, but in Windows NT 4.0, Microsoft added "font driver" support to allow ATM to provide Type 1 support (and in theory other font drivers for other types).