Rank: Member
Groups: Member
Joined: 3/18/2014
Posts: 15
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It's my understanding (feel free to correct me :-) that PDFs support multiple signings, in essence each additional signing signs the entire document before it.
However, if I try sign an already signed PDF the new signature reports as fine, but the original has an error: "SigDict/Contents illegal data" when I open the PDF in Acrobat. I've tried this with PDFs signed initially using EO, and also with a sample signed PDF from Adobe (http://blogs.adobe.com/security/SampleSignedPDFDocument.pdf)
I've attached the (doubly) signed PDF for you to see, this example uses a self-signed cert for the second signing, but the same thing happens with a trusted cert.
-Walden
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Rank: Administration
Groups: Administration
Joined: 5/27/2007
Posts: 24,196
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Hi,
Your understanding about multi-signature is correct. PDF should allow multiple signing because each new signature is appended to the file thus does not change anything before it, as such it should not invalidate the previously signed contents. Thus what you observed would appear to be a bug. If you can email us a test file (both before double signing and after double signing), we would be very happy to take a look.
Thanks!
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