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APPENDIX H                                  Compatibility and Implementation Notes



3.4.1, “File Header”
 13. Acrobat viewers require only that the header appear somewhere within
     the first 1024 bytes of the file.
 14. Acrobat viewers also accept a header of the form
     %!PS−Adobe−N . n PDF−M . m


3.4.3, “Cross-Reference Table”
 15. Acrobat viewers do not enforce the restriction on object numbers existing
     in more than one subsection; they use the entry in the first subsection
     where the object number is encountered. However, overlap is explicitly
     prohibited in cross-reference streams in PDF 1.5.
 16. Acrobat 6.0 and later do not use the free list to recycle object numbers;
     new objects are assigned new numbers.
 17. Acrobat viewers do not raise an error in cases where there are gaps in the
     sequence of object numbers between cross-reference subsections. The
     missing object numbers are treated as free objects.

3.4.4, “File Trailer”
 18. Acrobat viewers require only that the %%EOF marker appear somewhere
     within the last 1024 bytes of the file.

3.4.6, “Object Streams”
 19. When creating or saving PDF files, Acrobat 6.0 limits the number of ob-
     jects in individual object streams to 100 for linearized files and 200 for
     non-linearized files.

3.4.7, “Cross-Reference Streams” (Cross-Reference Stream Dictionary)
 20. FlateDecode is the only filter supported by Acrobat 6.0 and later viewers
     for cross-reference streams. These viewers also support unencoded cross-
     reference streams.

3.4.7, “Cross-Reference Streams” (Compatibility with PDF 1.4)
 21. Byte addresses can be as large as needed to address an arbitrarily large PDF
     file, regardless of the implementation limit for PDF integers in general.

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