SECTION 8.4
617
Anno ta tions
Many annotation types are defined as
markup annotations
because they are used
primarily to mark up PDF documents (see Table 8.20). These annotations have
text that appears as part of the annotation and may be displayed in other ways by
a viewer application, such as in a Comments pane.
Markup annotations can be divided into the following groups:
•
Free text annotations display text directly on the page. The annotation’s
Contents
entry specifies the displayed text.
•
Most other markup annotations have an associated pop-up window that may
contain text. The annotation’s
Contents
entry specifies the text to be displayed
when the pop-up window is opened. These include text, line, square, circle,
polygon, polyline, highlight, underline, squiggly-underline, strikeout, rubber
stamp, caret, ink, and file attachment annotations.
•
Sound annotations do not have a pop-up window but may also have associated
text specified by the
Contents
entry.
Note:
When separating text into paragraphs, a carriage return should be used (and
not, for example, a line feed character).
Note:
A subset of markup annotations are called
text markup annotations
(see
).
The remaining annotation types are not considered markup annotations:
•
The pop-up annotation type typically does not appear by itself; it is associated
with a markup annotation that uses it to display text.
Note:
The
Contents
entry for a pop-up annotation is relevant only if it has no par-
ent; in that case, it represents the text of the annotation.
•
For all other annotation types (
Link
,
Movie
,
Widget
,
PrinterMark
, and
TrapNet
),
the
Contents
entry provides an alternate representation of the annotation’s con-
tents in human-readable form, which is useful when extracting the document’s
contents in support of accessibility to users with disabilities or for other pur-
poses (see Section 10.8.2, “Alternate Descriptions”).