PDFlib 8 Windows COM/.NET Tutorial

5.5 Font Embedding and Subsetting
5.5.1 Font Embedding
PDF font embedding and font substitution in Acrobat. PDF documents can include
font data in various formats to ensure proper text display. Alternatively, a font descriptor
containing only the character metrics and some general font information (but not
the actual glyph outlines) can be embedded. If a font is not embedded in a PDF document,
Acrobat will take it from the target system if available and configured (»Use Local
Fonts«), or try to build a substitute font according to the font descriptor. The use of substitution
fonts results in readable text, but the glyphs may look different from the original
font. More importantly, Acrobat’s substitution fonts (AdobeSansMM and AdobeSerif-
MM) work only for Latin text, but not any other scripts or symbolic glyphs. Similarly,
substitution fonts don’t work if complex script shaping or OpenType layout features
have been used. For these reasons font embedding is generally recommended unless
you know that the documents are displayed on the target systems acceptably even
without embedded fonts. Such PDF files are inherently nonportable, but may be of use
in controlled environments, such as corporate networks where the required fonts are
known to be available on all workstations.
Embedding fonts with PDFlib. Font embedding is controlled by the embedding option
when loading a font (although in some cases PDFlib enforces font embedding):
font = p.load_font("WarnockPro", "winansi", "embedding");
Table 5.3 lists different situations with respect to font usage, each of which imposes different
requirements on the font and metrics files required by PDFlib. In addition to the
requirements listed in Table 5.3 the corresponding CMap files (plus in some cases the
Unicode mapping CMap for the respective character collection, e.g. Adobe-Japan1-UCS2)
must be available in order to use a (standard or custom) CJK font with any of the standard
CMaps.
Font embedding for fonts which are exclusively used for invisible text (mainly useful
for OCR results) can be controlled with the optimizeinvisible option when loading the
font.
Table 5.2 Different font usage situations and required files
font usage font metrics file required? font outline file required?
one of the 14 core fonts no only if embedding=true
TrueType, OpenType, or PostScript Type 1 host font installed
on the Mac or Windows system
no
no
non-core PostScript fonts yes only if embedding=true
TrueType fonts n/a yes
OpenType and SING fonts n/a yes
standard CJK fonts 1
no
no
1. See Section 6.5, »Chinese, Japanese, and Korean Text Output«, page 172, for more information on CJK fonts.
142 Chapter 5: Font Handling (Edition for COM, .NET, and REALbasic)