Re: [xep-support] PDF Accessibility?

From: Nikolai Grigoriev (
Date: Thu Dec 18 2003 - 07:41:14 PST

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    > I am having problems making PDFs generated from XEP (3.6)
    > accessible. I get the following error when trying to add tags
    > to the document in Acrobat 6:
    > "Bad PDF; could not read page structure. <Bad PDF; error
    > in processing fonts: cannot find CMap resource file>[1]"

    I believe the problem stays within Acrobat Make Accessible plug-in.
    The documentation for Acrobat 5.0 says:

    > - Font Encodings: The MakeAccessible Plug-In maps fonts
    > used in the document to a Unicode value. In some cases,
    > a font encoding used within a PDF document does not
    > contain enough information for the MakeAccessible
    > Plug-In to map to a Unicode equivalent.

    It looks like nothing changed in Acrobat 6.0.

    Apparently, MakeAccessible is confused by /Identity-H
    CMap that we use to specify encoding for TrueType fonts.
    I wonder why it does so: there is an explicit /ToUnicode
    CMap at each font descriptor. (You can test yourself
    that TrueType text in our PDF files can be searched
    and copied to the clipboard; this proves that the Unicode
    mapping information is already there).

    If I am right in my conclusions, the issue appears to be
    a real serious limitation of the plug-in. Have you spoken
    to Adobe about it?

    Right now, I see no alternative to using /Identity-H
    for TrueType fonts. The only suggestion that comes
    to mind: switch to Type1 fonts. They don't use CMaps:
    perhaps things will be easier there.

    > More generally, can anyone comment on XEP's support
    > (or lack thereof) for creating accessible PDFs?

    XEP 3.6 does not support tagged PDF out of the box.
    We have plans in this direction, but it will inevitably
    be a long run: tagging PDF is a tough task. (Adobe
    invented lots of tricky structures in the PDF, but
    didn't care even to define a standard character collection
    for plain Unicode. Sometimes, I have an impression
    that they deliberately complicate things for developers :-))

    Nikolai Grigoriev

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