But Adobe Acrobat allow to add watermark/annotation in this signed pdf and
after adding signature remains valid. can you guide me that how I can add
an Image in a signed pdf, either using watermark technique or annotation
and signature remain valid like Adobe Acrobat.
On Tue, Jan 29, 2013 at 1:35 PM, mkl <m...@wir-sind-cool.org> wrote:
> faisal,
>
> faisal wrote
> > I am trying to add watermark image in a digitally signed PDF using
> > itextsharp but after adding image Adobe Acrobat says that my signature is
> > invalid although I am adding in append mode. I have also checked the
> > internal PDF structure after adding image and the signature content is
> > intact (have no temper). can someone please guide me what is wrong in my
> > code?
>
> Already your implicit assumption taht you can apply a watermark to signed
> PDFs is wrong.
>
> A digital signature shall enable anyone to check whether the document was
> changed since signing or not. The signer can select a limited set of
> changes
> allowed to the document after his signature, but fundamentally changing the
> page content by adding an image never is allowed.
>
> You might want to check the PDF specification
>
> http://www.adobe.com/content/dam/Adobe/en/devnet/acrobat/pdfs/PDF32000_2008.pdf
> section 12.8 on digital signatures and, furthermore, the Adobe Technical
> White Paper "Adobe Acrobat 9 Digital Signatures, Changes and Improvements"
>
> http://wwwimages.adobe.com/www.adobe.com/content/dam/Adobe/en/devnet/reader/pdfs/readercomp_digitalsignatures.pdf
> section "Allowed and disallowed changes".
>
> Regards, Michael
>
>
>
> --
> View this message in context:
> http://itext-general.2136553.n4.nabble.com/Digital-Signature-Corrupted-after-adding-watermark-image-tp4657457p4657459.html
> Sent from the iText - General mailing list archive at Nabble.com.
>
>
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--
*Regards,*
*Faisal Raza Rana*
*Sr. Software Engineer/Technical Lead*
*Ascertia Ltd (www.ascertia.com)*
*40 Occam Road *
*Surrey Research Park Guildford Surrey, GU2 7YG*
*United Kingdom*
*+44 (0)1483 685500*
*+44 (0)1483 573704*
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MVC, Windows 8 Apps, JavaScript and much more. Keep your skills current
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iText(R) is a registered trademark of 1T3XT BVBA.
Many questions posted to this list can (and will) be answered with a reference
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Please check the keywords list before you ask for examples:
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