man-pages.7: Add some notes on generating optimal glyphs

Getting nice renderings of ^ ` and ~ requires special
steps in the page source.

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

man7/man-pages.7

@@ -902,7 +902,8 @@ Some examples:
 .PP
 Finally, note that "re-create" and "recreate" are two different verbs,
 and the former is probably what you want.
-.SS Real minus character
+.\"
+.SS Generating optimal glyphs
 Where a real minus character is required (e.g., for numbers such as \-1,
 for man page cross references such as
 .BR utf\-8 (7),
@@ -913,9 +914,9 @@ use the following form in the man page source:
     \e\-
 .PP
 This guideline applies also to code examples.
-.SS Character constants
-To produce single quotes that render well in both ASCII and UTF-8,
-use the following form for character constants in the man page source:
+.PP
+To produce unslanted single quotes that render well in ASCII, UTF-8, and PDF,
+use "\e(aq" ("apostrophe quote"); for example
 .PP
     \e(aqC\e(aq
 .PP
@@ -923,6 +924,17 @@ where
 .I C
 is the quoted character.
 This guideline applies also to character constants used in code examples.
+.PP
+Where a proper caret (\(ha) that renders well in both a terminal and PDF
+is required, use "\\(ha".
+This is especially necessary in code samples,
+to get a nicely rendered caret when rendering to PDF.
+.PP
+Using a naked "\(ti" character results in a poor rendering in PDF.
+Instead use "\\(ti".
+This is especially necessary in code samples,
+to get a nicely rendered tilde when rendering to PDF.
+.\"
 .SS Example programs and shell sessions
 Manual pages may include example programs demonstrating how to
 use a system call or library function.