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SECTION 8.4                                                             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
“Text Markup Annotations” on page 633).

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”).

Table 8.21 lists entries that apply to all markup annotations.

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