Previous Next

                                                           97
          SECTION 3.4                                                                     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
                 << key1 value1
                     key2 value2
                     …
                     keyn valuen
                 >>
             startxref
             Byte_offset_of_last_cross-reference_section
             %%EOF

          Table 3.13 lists the contents of the trailer dictionary.

                               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.

Root       dictionary       (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”).

Encrypt    dictionary       (Required if document is encrypted; PDF 1.1) The document’s encryption dictionary
                            (see Section 3.5, “Encryption”).

Info       dictionary       (Optional; must be an indirect reference) The document’s information dictionary
                            (see Section 10.2.1, “Document Information Dictionary”).

Previous Next