CHAPTER 3
96
Syntax
are free (objects number 0 and 3). Object number 3 has been deleted, and the
next object created with that object number is given a generation number of 7.
Example 3.5
xref
0 6
0000000003
0000000017
0000000081
0000000000
0000000331
0000000409
65535
00000
00000
00007
00000
00000
f
n
n
f
n
n
total of five entries. The first subsection contains one entry, for object number 0,
which is free. The second subsection contains one entry, for object number 3,
which is in use. The third subsection contains two entries, for objects number 23
and 24, both of which are in use. Object number 23 has been reused, as can be
seen from the fact that it has a generation number of 2. The fourth subsection
contains one entry, for object number 30, which is in use.
Example 3.6
xref
0 1
0000000000
3 1
0000025325
23 2
0000025518
0000025635
30 1
0000025777
65535 f
00000 n
00002 n
00000 n
00000 n
See Section G.6, “Updating Example,” for a more extensive example of the
structure of a PDF file that has been updated several times.
3.4.4 File Trailer
The
trailer
of a PDF file enables an application reading the file to quickly find the
cross-reference table and certain special objects. Applications should read a PDF