An abbreviation and
filename extension for
Printer Font Metrics file, which is used with
Type 1 fonts. These files coexist with related
PFB files, and together represent a single typeface. PFM files contain data used to display a
font on-screen. Type managers use this
vector data and
rasterize it. It then
scales the image to the proper size and
smooths the edges.
Multiple master fonts do not use PFM files, they use a somewhat similar file called a Multiple Master Metrics (MMM) file.
Compare with TrueType fonts, which contain both the screen and printer data in a single file.