5 符号¶
Notation
PDF 操作符、PDF 关键字、PDF 字典中的键名称以及其他预定义名称都使用粗体无衬线字体书写；表示 PDF 操作符的操作数或字典键的值的单词使用斜体无衬线字体书写。
在 7.2 节 "词汇约定" 中定义的用于分隔对象和描述 PDF 文件结构的标记字符，可以通过它们在 ANSI X3.4-1986（ASCII 7 位美国代码）中的字符名称，用大写粗体无衬线字体书写，后跟括号中的两位十六进制字符值，并带有 "h" 后缀来标识。
在 7.9.2 节 "字符串对象类型" 中定义的文本流中的字符，可以通过它们在 ANSI X3.4-1986（ASCII 7 位美国代码）中的字符名称，用大写无衬线字体书写，后跟括号中的四位十六进制字符代码值，并带有 "U+" 前缀来标识，如本条款中的示例 1 所示。
示例 1：EN SPACE (U+2002)。
PDF operators, PDF keywords, the names of keys in PDF dictionaries, and other predefined names are written in bold sans serif font; words that denote operands of PDF operators or values of dictionary keys are written in italic sans serif font.
Token characters used to delimit objects and describe the structure of PDF files, as defined in 7.2, "Lexical Conventions", may be identified by their ANSI X3.4-1986 (ASCII 7-bit USA codes) character name written in upper case in bold sans serif font followed by a parenthetic two digit hexadecimal character value with the suffix “h”.
Characters in text streams, as defined by 7.9.2, "String Object Types", may be identified by their ANSI X3.4- 1986 (ASCII 7-bit USA codes) character name written in uppercase in sans serif font followed by a parenthetic four digit hexadecimal character code value with the prefix “U+” as shown in EXAMPLE 1 in this clause.
EXAMPLE 1 EN SPACE (U+2002).