Fonts in PDF files
A font object in PDF is a description of a digital typeface. It may either describe the characteristics of a typeface, or it may include an embedded font file. This article shows an overview of fonts supported in PDF files.
Basic of PDF Fonts
The PDF file format supports the use of the following font formats:
- Type 1
- Type 3
- Composite fonts (Type 0): both Type 1 (CIDFontType0) and TrueType (CIDFontType2) are supported.
- OpenType: From PDF 1.6 onwards, OpenType fonts can be stored directly in PDF files. In prior releases OpenType fonts are embedded as either Type 1 or TrueType fonts. The ability to embed OpenType directly was added for the forms capabilities of PDF, it offers no immediate advantage for prepress users.
Embedding and Subsetting
By preference any fonts that are used in a layout are also included in the PDF file itself. This makes sure that the file can be viewed and printed as it was created by the designer. There are two mechanisms to include fonts in a PDF:
Embedding – A full copy of the entire character set of a font is stored in the PDF.
Subsetting – Only those characters that are actually used in the lay-out are stored in the PDF. If the “M” character doesn't appear anywhere in the text, that character is not included in the font. This means that PDF files with subsetted fonts are smaller than PDF files with embedded fonts.
Click here to learn how to embed or subset fonts in a PDF file.
If certain fonts are missing from the PDF file, Adobe Acrobat and Adobe Reader will automatically try to emulate the missing font by using one of the Multiple Master fonts that are built into these programs. This way, the document will not be represented exactly as the designer wanted it to, but at least the text won’t reflow. The Multiple Master fonts that are used for this are:
- Adobe Serif MM
- Adobe Sans MM
Another important aspect of font handling is the encoding. This refers to the mapping of a character code to a particular glyph (character shape) description. Each font in a PDF uses a specific type of encoding, either a standard one or a custom one. The following types of encoding are supported by the PDF file format:
- A custom encoding can be used by defining a 'Differences Array'.
Fonts that are not necessarily included in PDF files
Specific common Type 1 fonts installed as a part of the Adobe Acrobat installation are the Base 14 Fonts. By default, when creating a Screen Optimized PDF with Distiller or any PDF from PDF Writer, the Base 14 Fonts are not embedded in the document. Since these fonts are available in Acrobat Reader it is assumed that they will be available to any viewer and embedding would simply add unnecessarily to the file size.
- Courier, Courier-Bold, Courier-Oblique & Courier-BoldOblique
- Times-Roman , Times-Bold , Times-Italic & Times-BoldItalic
- Helvetica, Helvetica-Bold, Helvetica-Oblique & Helvetica-BoldOblique