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> >I'm up against a rather thorny problem. Signatures are > destroyed in the > >presence of the "NeedAppearances" flag. > > Quite true, and quite expected since you/Acrobat is > modifying the > file so the signature is now invalid. I'm making "append" changes, so the signature is still valid over its original byte range. When you open a signed PDF with an FDF _that_changes_field_values_ the signature is still considered valid, though you do receive a warning that the file has been changed since it was signed. I don't see why post-NeedAppearances PDFs should be any different. Even if the above weren't the case, I would expect the signatures to be marked as _invalid_ rather than being damaged or removed entirely. Invalid? Sure. MISSING?! That's just weird (frustrating, maddening, infuriating, ... ) It's this kind of inconsistent behavior that really makes me... "dislike"... Acrobat forms. > Also, keep in mind that not all versions of Acrobat > fully support the NeedAppearances flag in all cases > - which is why you shouldn't rely on it and should > instead be generating your own appearances! I do agree that some viewers aren't capable of rendering appearances... that's why our products specifically state what viewers support. Between NeedsAppearances and various JavaScript issues, supporting a wide variety of viewers is simply out of the question. I'd love to be generating my own appearances, but there are two considerations that make it impractical this go-round: 1) Time 2) Time Heh. Development time and execution time. There was never room in the schedule for me to implement this (along with a "ground up" java pdf read-write beasty that supported crypto, along with all the other miscellany on my plate). Further, this code is executed server-side and it just makes sense to distribute that particular load to the clients. The "development time" issue can be solved by pushing that feature off to a later version... but the execution time problem isn't so easily solved. So the question remains... how can I preserve signatures in the presence of the NeedAppearances flag /on the Acrobat 5 and 6 viewer families/? --Mark Storer Software Engineer Cardiff Software #include <disclaimer> typdef std::disclaimer<Cardiff> Discard; To change your subscription: http://www.pdfzone.com/discussions/lists-pdfdev.html
