Adobe Acrobat is bundled with some of the new Apple Macintosh computers. It installs the substitution fonts Adobe Sans MM and Adobe Serif MM for rendering the fonts to create Portable Document Format (PDF) files. These fonts are called Multiple Master Fonts (MMF) and are not the standard type fonts that would show up in the fonts menu.
Multiple Master Fonts is a font technology that lets you create thousands of font instances, the way the character looks, from a single typeface. Multiple Master Fonts design includes one or more design axis; including weight, width, style, and optical size. This provides solutions to common but hard-to-fix page composition problems such as copy fitting that otherwise cannot be solved without artificially squeezing, stretching, or compromising the type.