SECTION 3.4
97
File Structure
file from its end. The last line of the file contains only the end-of-file marker,
%%EOF
. (See implementation note 18 in Appendix H.) The two preceding lines
contain the keyword
startxref
and the byte offset from the beginning of the file to
the beginning of the
xref
keyword in the last cross-reference section. The
startxref
line is preceded by the
trailer dictionary,
consisting of the keyword
trailer
followed by a series of key-value pairs enclosed in double angle brackets
(
<<
…
>>
). Thus, the trailer has the following overall structure:
trailer
<<
key
1
value
1
key
2
value
2
…
key
n
value
n
>>
startxref
Byte_offset_of_last_cross-reference_section
%%EOF
TABLE 3.13 Entries in the file trailer dictionary
KEY
TYPE
VALUE
Size
integer
(Required; must not be an indirect reference)
The total number of entries in the file’s
cross-reference table, as defined by the combination of the original section and all
update sections. Equivalently, this value is 1 greater than the highest object number
used in the file.
Note:
Any object in a cross-reference section whose number is greater than this value is
ignored and considered missing.
Prev
integer
(Present only if the file has more than one cross-reference section; must not be an indi-
rect reference)
The byte offset from the beginning of the file to the beginning of the
previous cross-reference section.
(Required; must be an indirect reference)
The catalog dictionary for the PDF docu-
ment contained in the file (see Section 3.6.1, “Document Catalog”).
(Required if document is encrypted; PDF 1.1)
The document’s encryption dictionary
(see Section 3.5, “Encryption”).
(Optional; must be an indirect reference)
The document’s information dictionary
(see Section 10.2.1, “Document Information Dictionary”).
Root
dictionary
dictionary
dictionary
Encrypt
Info