Home » Newsletter » March 2019

By Santhanam L

PDF is a fixed document format and also one of the Page Description Languages that describes how the elements on a page, such as text, shapes/line-art, image, etc., should be represented so that they look the same regardless of the software, hardware, or operating system they are being viewed on. In order to represent a text element on a page a font is required along with a specified character encoding standard.

Encoding Standard

A character encoding standard specifies how to translate the numeric value of the characters in a text into visible characters. For instance, WinAnsi encoding standard translates the numeric decimal value 174 into ® (registered) character whereas, MacRoman encoding standard translates the same numeric decimal value 174 into Æ (AE) character.

The character encoding types supported by PDF format are
WinAnsi, MacRoman, MacExpert, Standard encoding, PDFDocEncoding, Built-in, Identity-(H/V), and CJK encoding.

Note: Built-in type is not the name of the encoding but it specifies that the encoding is built into the font.

Font and Typeface

A font is a collection of characters with a similar design. A typeface (also known as font family) is a set of one or more fonts each composed of glyphs (representation of a readable character) that share common design features. Each font of a typeface has a specific weight, style, condensation, width, slant, italicization, and many other characteristics. For instance, the typeface Arial may include the fonts Arial Regular, Arial Bold, Arial Italic, etc. Typefaces are developed using various outline font standards such as Type1, TrueType, etc.

There are 8 font standards supported by the PDF format:
Type1, CFF, Multiple master, TrueType, OpenType, Type3, Type 0 CIDFont, and Type 2 CIDFont.

Font+Encoding combinations possible for representation of text content in PDF

The following table lists the possible/supported Encoding standard types for each Font standard supported in PDF.

Font standard types (number of supported encodings)	Supported Encoding standard types by the Font standard
Type1 (5)	WinAnsiEncoding, MacRomanEncoding, MacExpertEncoding, StandardEncoding, and built-in encoding
CFF (Type 1–equivalent font program) (5)	WinAnsiEncoding, MacRomanEncoding, MacExpertEncoding, StandardEncoding, and built-in encoding
Multiple master (Extension of Type1 font) (5)	WinAnsiEncoding, MacRomanEncoding, MacExpertEncoding, StandardEncoding, and built-in encoding
TrueType (3)	WinAnsiEncoding, MacRomanEncoding, and built-in encoding
OpenType (Extension of TrueType font) (3)	WinAnsiEncoding, MacRomanEncoding, and built-in encoding
Type3 (glyph descriptions are defined by streams of PDF graphics operators) (1)	always built-in encoding
Type 0 CIDFont (glyph descriptions based on CFF) (2)	Identity, and CJK encoding
Type 2 CIDFont (glyph descriptions based on the TrueType glyph technology) (2)	Identity, and CJK encoding

Thus, there are totally twenty six (26) Font+Encoding combinations supported in PDF.

The following screenshot shows text drawn on a PDF page using different Font+Encoding combinations.

References:

• PDF Specification v2.0 (ISO/DIS 32000-2.3)
• https://support.office.com/en-us/article/choose-text-encoding-when-you-open-and-save-files-60d59c21-88b5-4006-831c-d536d42fd861
• https://en.wikipedia.org/wiki/Typeface