Adobe Acrobat SDK
Implementation Notes
Adobe® Supplement to the ISO 32000
Implementation Notes to the PDF Reference, sixth edition 115
Acrobat 5 and later viewers do not give special treatment to any font. Any non-embedded font, regardless
of name, will be processed in the same way.
5.5.3 Font Subsets
63. For Acrobat 3.0 and earlier viewers, all font subsets whose
BaseFont
names differ only in their tags
should have the same font descriptor values and should map character names to glyphs in the same
way; otherwise, glyphs may be shown unpredictably. This restriction is eliminated in Acrobat 4.0.
5.5.4 Type 3 Fonts
64. In principle, the value of the
Encoding
entry could also be the name of a predefined encoding or an
encoding dictionary whose
BaseEncoding
entry is a predefined encoding. However, Acrobat 4.0 and
earlier viewers do not implement this correctly.
65. For compatibility with Acrobat 2.0 and 2.1, the names of resources in a Type 3 font’s resource dictionary
must match those in the page object’s resource dictionary for all pages in which the font is referenced.
If backward compatibility is not required, any valid names may be used.
5.6.4 CMaps
66. Embedded CMap files, other than
ToUnicode
CMaps, do not work properly in Acrobat 4.0 viewers; this
has been corrected in Acrobat 4.05.
67. Japanese fonts included with Acrobat 6.0 contain only glyphs from the Adobe Japan1-4 character
collection. Documents that use fonts containing additional glyphs from the Adobe-Japan1-5 collection
must embed those fonts to ensure proper display and printing.
5.7 Font Descriptors
68. Acrobat viewers earlier than version 3.0 ignore the
FontFile3
entry. If a font uses the Adobe standard
Latin character set (as defined in Section D.1, “Latin Character Set and Encodings”), Acrobat creates a
substitute font. Otherwise, Acrobat displays an error message (once per document) and substitutes any
characters in the font with the bullet character.
5.8 Embedded Font Programs
69. For simple fonts, font substitution may be performed using multiple master Type 1 fonts. This
substitution can be performed only for fonts that use the Adobe standard Latin character set (as
defined in Section D.1, “Latin Character Set and Encodings”). In Acrobat 3.0.1 and later, Type 0 fonts that
use a CMap whose
CIDSystemInfo
dictionary defines the Adobe-GB1, Adobe-CNS1 Adobe-Japan1,
or Adobe-Korea1 character collection can also be substituted. To make a document portable, fonts that
cannot be substituted must be embedded.
6.4.2 Spot Functions
70. When Distiller encounters a call to the PostScript
setscreen
or
sethalftone
operator that includes
a spot function, it compares the PostScript code defining the spot function with that of the predefined
spot functions shown in Table6.1. If the code matches one of the predefined functions, Distiller puts
the name of that function into the halftone dictionary; Acrobat uses that function when printing the
PDF document to a PostScript output device. If the code does not match any of the predefined spot
