SECTION 3.6
149
Document Structure
Inheritance of Page Attributes
Some of the page attributes shown in Table 3.27 are designated as
inheritable.
If
such an attribute is omitted from a page object, its value is inherited from an
ancestor node in the page tree. If the attribute is a required one, a value must be
supplied in an ancestor node. If the attribute is optional and no inherited value is
specified, the default value is used.
An attribute can thus be defined once for a whole set of pages by specifying it in
an intermediate page tree node and arranging the pages that share the attribute as
descendants of that node. For example, a document might specify the same
media box for all of its pages by including a
MediaBox
entry in the root node of
the page tree. If necessary, an individual page object could override this inherited
value with a
MediaBox
entry of its own.
Note:
In a document conforming to the Linearized PDF organization (see Appen-
naries to which they apply; they may not be inherited from an ancestor node.
2, and 4 are rotated clockwise by 90 degrees, page 3 by 270 degrees, page 6 by 180
degrees, and pages 5 and 7 not at all (0 degrees).
Pages
Pages
/Rotate 90
Pages
Pages
/Rotate 180
Page
Page 1
Page
Page 2
Pages
Page
Page 5
Page
Page 6
Page
/Rotate 0
Page 7
Page
/Rotate 270
Page 3
Page
/Rotate 90
Page 4
FIGURE 3.6
Inheritance of attributes