Signatures and Version

  • Anonymous

    Anonymous - 2012-11-19

    I have a PDF with already a Signature.
    I want to add pages below, creating a new version of the document, wich will then be signed by someone else.
    However, when i add pages, the first signature gets corrupted.

    How can we manage the versions/revisions ?

  • mtraut

    mtraut - 2012-11-23

    PDF has the concept of "incremental save".  As long as you keep the original file bytewise the same and only add/change COSObjects, your original signature remains intact and a new signature cen be added. This incremental save is the default with jPod.

    BTW what do you mean with "corrupted". The signature will be void if you change anything in the original byte stream. If you add/change objects CORRECTLY, the original signature will still be flagged with a warning by tools like the Reader. It is mathematical correct, but the reader will bug you with "the document has changed". You can not change this behavior.

    There's a special and quite complex specification in newer PDF versions on how to create signatures that themselve contain information for the Reader what further changes are allowed and are not to be flagged. But this is beyond this forum… and it has to be planned from the start - a document containing some basic signature can not be converted to this "workflow mode".


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