Hi,
We've been investigating the latest version of GroupDocs.Signature
for .net using your example console applications in GitHub (https://github.com/groupdocs-signature/GroupDocs.Signature-for.NET).
When we "digitally" sign a PDF document, then open
the resulting file in Adobe Reader XI, the certification block field is
detected and seems to work correctly. However, in our product
workflow, multiple people may be required to sign the same document. PDFs
do not appear to accept having a document certified multiple times (the
previous certification that becomes invalid causes a big "not
valid" error at the top of the page).
Is there any way to
place Signature field(s) before certifying the document, so that multiple
people can sign? ("Sign with text" appears to just place a text
field, rather than being a signature field)
Cheers,
Hi Timothy,
Thanks for taking interest in GroupDocs.Signature for .NET.
the previous certification that becomes invalid causes a big “not valid” error at the top of the page
We are able to reproduce this issue at our end. Hence, it’s been logged in our internal issue tracking system. As we get any update on this issue from the concerned team, we will inform you.
As far as your second question is concerned:
Is there any way to place Signature field(s) before certifying the document, so that multiple people can sign? (“Sign with text” appears to just place a text field, rather than being a signature field)
Can you please elaborate it a bit more. Do you get invalid signed/certified document when you do multiple text signatures and then do digital signature?
Many Thanks
Hi Arir,
Thanks for getting back
to me.
"Do you get invalid
signed/certified document when you do multiple text signatures and then do
digital signature?"
Adding GroupDocs
"text" style signatures, then a "digital" style signature
works without any errors. However, the "text" style
signatures do not involve a digital certificate, so do not track or verify the
document at the point that the user "signed" it.
We have been playing
with the manual signing features in Adobe Reader XI - if you use the
"Fill & Sign" sidebar, then the "Work with
Certificates" section, it shows the options for "Certify" and
also "Sign with Certificate". We dug a bit further into PDF
digital signatures, and found this reference: From: https://www.adobe.com/devnet-docs/acrobatetk/tools/DigSig/Acrobat_DigitalSignatures_in_PDF.pdf
It indicates:
PDF defines two types of
signatures: approval and certification. Both types are byte range signatures
over all file contents. Both take a visual snapshot of the document at the time
it was signed and thus provide a high level of document integrity.
The differences are as
follows:
- Approval: There can be
any number of approval signatures in a document.
- Certification: There
can be only one certification signature and it must be the first one in a
document.
It appears that
the GroupDocs "digital" style signature is the
"Certification" type, and it sounds like what we're after is the
"Approval" type - and ideally both. That way we could
certify the document, then place Approval signatures for potentially several
people.
Unfortunately it appears
that there's no capacity for GroupDocs to add "Approval" fields at
the moment, unless we missed something?
Cheers,
Tim
Hi Timothy,
options for “Certify” and also “Sign with Certificate”
We would like to apprise you that you can do image signature with digital certificate. You may find this
documentation helpful.
As far as text signature with digital certificate is concerned, we have generated an investigation ticket in our internal issue tracking system. As we’ll have any update, we will guide you accordingly.
Many Thanks
Hi Atir,
Thanks again for
your reply. Including an image when using "digital sign" is
certainly available, but unfortunately we'd still run into the problem that we
can't use that approach multiple times on the same document.
We'll continue to
investigate our options, but will keep an eye on this post in case there's any
new information.
Cheers,
Tim
Hi Timothy,
We are still investigating this issue. As we have any update, we shall notify you.
Best Wishes
Hi Timothy,
We are pleased to inform you that your reported issue “Impose text signature with digital signature/certificate” has been resolved, please follow the given resources in order to embed/explore this feature:
However, your other reported issue “Digitally signed PDF document shows invalid certification” will be resolved in upcoming release of the API.
Best regards