Multiple People Signing a PDF


#1

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,


#2

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




#3

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


#4

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

#5

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


#6

Hi Timothy,


We are still investigating this issue. As we have any update, we shall notify you.

Best Wishes

#7

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