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                                APPENDIX C


           CImplementation Limits

In general, PDF does not restrict the size or quantity of things described in the
file format, such as numbers, arrays, images, and so on. However, a PDF consum-
er application running on a particular processor and in a particular operating en-
vironment does have such limits. If an application attempts to perform an action
that exceeds one of the limits, it displays an error.

PostScript interpreters also have implementation limits, listed in Appendix B of
the PostScript Language Reference, Third Edition. It is possible to construct a PDF
file that does not violate application limits but does not print on a PostScript
printer. Keep in mind that these limits vary according to the PostScript Lan-
guageLevel, interpreter version, and the amount of memory available to the inter-
preter.

This appendix describes typical limits for Acrobat. These limits fall into two main
classes:

• Architectural limits. The hardware on which a viewer application executes im-
  poses certain constraints. For example, an integer is usually represented in 32
  bits, limiting the range of allowed integers. In addition, the design of the soft-
  ware imposes other constraints, such as a limit to the number of elements in an
  array or string.
• Memory limits. The amount of memory available to a viewer application limits
  the number of memory-consuming objects that can be held simultaneously.

PDF itself has one architectural limit: Because ten digits are allocated to byte off-
sets, the size of a file is limited to 1010 bytes (approximately 10 gigabytes).

Table C.1 describes the architectural limits for Acrobat viewer applications run-
ning on 32-bit machines. Because Acrobat implementations are subject to these


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