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PDF20 Spec 09 Text Strings
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9.5
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Introduction to font data structures
A font shall be represented in PDF as a dictionary specifying the type of font, its PostScript language name, its encoding, and information that can be used to provide a substitute when the font program is not available. Optionally, the font program (more commonly known as font files) may be embedded as a stream object in the PDF file. NOTE 1
See 9.2, "Organisation and use of fonts" for more introductory information.
"Table 108 — Font types" lists the types of fonts that are supported in ISO 32000 along with the value that shall be used for the Subtype key in the font dictionary that represents the font. No values for Subtype other than those listed in the table are valid. Type 0 fonts are called composite fonts; other types of fonts are called simple fonts. In addition to fonts, PDF supports two classes of font-related objects, called CIDFonts and CMaps, described in 9.7.2, "CID-Keyed fonts overview". CIDFonts are listed in "Table 108 — Font types" because, like fonts, they are collections of glyphs; however, a CIDFont shall not be used directly but only as a component of a Type 0 font. © ISO 2020 – All rights reserved
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ISO 32000-2:2020(E)
Table 108 — Font types
NOTE 2
Type
Subtype Value
Description
Type 0
Type0
(PDF 1.2) A composite font — a font composed of glyphs from a descendant CIDFont (see 9.7, "Composite fonts")
Type 1
Type1
A font that defines glyph shapes using Type 1 font technology (see 9.6.2, "Type 1 fonts").
MMType1
A multiple master font — an extension of the Type 1 font that allows the generation of a wide variety of typeface styles from a single font (see 9.6.2.3, "Multiple master fonts")
Type 3
Type3
A font that defines glyphs with streams of PDF graphics operators (see 9.6.4, "Type 3 fonts")
TrueType
TrueType
A font based on the TrueType font format (see 9.6.3, "TrueType fonts") and with glyph descriptions based on TrueType glyph technology.
CIDFont
CIDFontType0
(PDF 1.2) A CIDFont whose glyph descriptions are based on CFF font technology (see 9.7.4, "CIDFonts")
CIDFontType2
(PDF 1.2) A CIDFont whose glyph descriptions are based on TrueType glyph technology (see 9.7.4, "CIDFonts")
Embedding of OpenType font programs (files) in PDF is described in "Table 124 — Embedded font organisation for various font types" when the value of the FontFile3 key is OpenType. The font dictionary that refers to it can have a Subtype of TrueType, Type1, CIDFontType0, or CIDFontType2, depending upon the glyph technology used in the OpenType font and other details provided in that table.
For all font types, the term font dictionary refers to a PDF dictionary containing information about the font; likewise, a CIDFont dictionary contains information about a CIDFont. Except for Type 3, this dictionary is distinct from the font program that defines the font’s glyphs. That font program may be embedded in the PDF file as a stream object or be obtained from some external source. NOTE 3
This terminology differs from that used in the PostScript language. In PostScript, a font dictionary is a PostScript data structure that is created as a direct result of interpreting a font program. In PDF, a font program is always treated as if it were a separate file, even when its content is embedded in the PDF file. The font program is interpreted by a specialised font interpreter when necessary; its contents never materialize as PDF objects.
NOTE 4
Most font programs (and related programs, such as CIDFonts and CMaps) conform to external specifications, such as the Adobe Type 1 Font Format. This document does not include those specifications. See 2, "Normative references" for more information about the specifications mentioned in this clause.
NOTE 5
The most predictable and dependable results are produced when all font programs used to show text are embedded in the PDF file. See 9.9, "Embedded font programs" for the precise description of how to do so. If a PDF file refers to font programs that are not embedded, the results depend on the availability of fonts in the PDF processor’s environment. See 9.8, "Font descriptors" for some conventions for referring to external font programs. However, some details of font naming, font substitution, and glyph selection are implementation-dependent and can vary among different PDF processors and operating system environments.
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© ISO 2020 – All rights reserved
ISO 32000-2:2020(E)
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