Tamas,
Tamas wrote:
>
> How can I appen an existing PDF with some kind of content (e.g Image) in a
> way sush that the new content has incremented generation number and the
> signature of the original contents (with the previous generation number)
> stays valid?
>
I'm afraid, iText does not itself generate objects with generation numbers
greater than 1. Hardly any PDF tool does, by the way.
This does not influence the validity of your signatures, though.
If you check the validity using iText, all your signatures should verify
just fine as you stamp in append mode.
If you check the validity using Adobe products, you either get a warning or
actually an error, depending on the version of those products you use. This
is due to what Adobe considers valid changes allowed after a signature is
applied.
Tamas wrote:
>
> iterate
> {
> The receiver person opens the PDF, modifies it (adding tables, images or
> comments) and signes the PDF doc with the "tool".
> The doc is forwarded to the next person.
> }
>
This does not sound like you respect the concept of allowed and disallowed
changes. Therefore, Adobe products likely will reject your signatures.
Tamas wrote:
>
> At the end of the process the PDF contains all of the versions and
> signetures belongs to the actual version created before.
> [...]
> The problem is that, the generation number of the image stays '0', so the
> first signature will be invalid.
> Please see the attached pdf files! ( 17 0 obj <</...)
>
The generation number does not reflect the document revision the object
belongs to. The revision an object belongs to only depends on its position
in the file.
The reason for the invalidity most likely is that the way you add the image
is recognized as a disallowed change by Adobe products.
Regards, Michael.
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Sent from the iText - General mailing list archive at Nabble.com.
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