Bitstream's TrueDoc Portable Font Resource format is part of several digital TV broadcast specifications and is documented as RFC 3073: https://datatracker.ietf.org/doc/html/rfc3073
Magic number(s): 50 46 52 30 hex
File extension(s): PFR
Macintosh File Type Code(s): Creator: 'b$pw' Type: 'PFR 'There is also a newer version of the format with 50 46 52 31 hex (PFR1),
such as the test file included here. libmagic also recognizes PFR1:
https://github.com/file/file/blob/7a821aedc144f70ec848ea632a64db74b79563c1/magic/Magdir/fonts#L249-L252
The Bitstream specifications are available from Wayback Machine: https://web.archive.org/web/20040407162455/http://www.bitstream.com/categories/developer/truedoc/pfrspec.html
"The PFR specification defines the Bitstream portable font resource (PFR), which is a compact, platform-independent format for representing high-quality, scalable outline fonts. Many independent organizations responsible for setting digital TV standards have adopted the PFR font format as their standard font format, including:
- ATSC (Advanced Television Systems Committee)
- DAVIC (Digital Audio Visual Council)
- DVB (Digital Video Broadcasting)
- DTG (Digital TV Group)
- MHP (Multimedia Home Platform)
- ISO/IEC 16500-6:1999
- OCAP (OpenCable Application Platform)"
Per RFC 3073, "The PFR media type has been previously registered with IANA as
application/vnd.truedoc. In view of its subsequent widespread adoption as
a standard font format by multiple standards bodies who have relationships with
the Internet community, Bitstream has been asked to re-register this media type
within the IETF tree."
https://www.iana.org/assignments/media-types/application/vnd.truedoc
http://www.iana.org/assignments/media-types/application/font-tdpfr
This format was once supported for downloadable web fonts in Netscape 4.x.