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APPENDIX H                                    Compatibility and Implementation Notes



      specified by the EFF entry. In both Acrobat 6.0 and 7.0, if the security han-
      dler indicates that document-level metadata is to be in plaintext, the meta-
      data will not be encrypted. It is up to individual security handlers to store
      their own flags that indicate whether document-level metadata should be
      in plaintext.
 30. Acrobat viewers do not support the ability for third-party security han-
     dlers to specify None as a value for CFM.
 31. In the file specification dictionary (see Section 3.10.2, “File Specification
     Dictionaries”), related files (RF) must use the same crypt filter as the em-
     bedded file (EF).
 32. The value of the EncryptMetadata entry is set by the security handler
     rather than the Acrobat viewer application.

3.6.1, “Document Catalog”
 33. Acrobat 5.0 and Acrobat 6.0 avoid adding a Version entry to the document
     catalog and do so only if necessary. Once they have added this entry, they
     behave in this way:
      • Acrobat 5.0 never removes the Version entry. For documents containing
        a Version entry, Acrobat 5.0 attempts to ensure that the version specified
        in the header matches the version specified in the Version entry; if this
        is not possible, it at least ensures that the latter is later than (and there-
        fore overrides) the version specified in the header.
      • Acrobat 6.0 removes the Version entry when doing a full (non-incre-
        mental) save of the document.
 34. In PDF 1.2, an additional entry in the document catalog, named AA, was
     defined but was never implemented. The AA entry that is newly intro-
     duced in PDF 1.4 is entirely different from the one that was contemplated
     for PDF 1.2.

3.6.2, “Page Tree” (Page Objects)
 35. In PDF 1.2, an additional entry in the page object, named Hid, was defined
     but was never implemented. Beginning with PDF 1.3, this entry is obso-
     lete and should be ignored.
 36. Acrobat 5.0 and later viewers do not accept a Contents array containing
     no elements.

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