4 Replies Latest reply on May 17, 2013 12:30 AM by GarryBW

    Stringing a number of Digitally signed documents together


      Hi, I am currently running a project to convert my companies hard copy documentation packs to fully electronic, digitally signed documents.


      The final document will be a string of several digitally signed documents combined together in one final document for presentation to our customers. I am currently having diffuculty retaining the original digital signature of the documents when they are combined.


      I am using Acrobat Pro XI and have tried Certifying and just digitally signing but the original signatures appear to be deleted in the final document.


      The real world application will be the initial company signing their docs for authentication and email it to their customer, this company will add docs to this first file and sign it then forward this on to their customer, etc until it reaches me when the completed document file will be locked.


      Can anyone point me in the right direction?

        • 2. Re: Stringing a number of Digitally signed documents together
          GarryBW Level 1

          Thanks,   I finally worked it out. However, it's not an ideal format for how I originally visualised the outcome.    From what I have read on the Adobe site and the discussion threads it doesn't appear that you can combine several digitally signed documents together to make a single document pack.


          I had hoped that there was some way to have, say, 3 documents digitally signed by different people then merge these together into a single document but still retaining their individual signature details. This final document could then be certified by myself as the final recipient.


          This final document pack could then be added to the final customers portfolio with many other documents.


          The only way i can see to do this at the moment is to "sign" the documents with an annotation (ie. a JPG or PDF stamp), or use the built in stamps in COMMENTS, combine these into a single document and then digitally sign / certify this completed pack.


          Has any one encountered this situation before and managed to solve it?


          I understand that, because a change has been made to the original document this nullifies the orignal digital signature. I could live with this as long as I could retain the signatories details on that document.

          • 3. Re: Stringing a number of Digitally signed documents together
            IsakTen Level 4

            A Digital PKI-based signature in PDF is based on the byte range of the signature content in the PDF file. If you move these bytes, the signature becomes unuasable. When you combine, say, 3 PDFs into one, the byte positions of the signatures in the 2nd and 3rd PDFs change, which makes these signatures unusable. This is why Acrobat's "Inset Pages" feature does not allow you to insert pages from/to digitally signed PDFs. There are other Acrobat features that also do not work with signed PDFs.
            If you are fine with non-digital signatures, like stamps, this is a completely different story. There is a distinction between digital and electronic signatures. The former are PKI-based whereas the latter in many cases are not. You need to be clear on which signature types you need and act accordingly.

            • 4. Re: Stringing a number of Digitally signed documents together
              GarryBW Level 1

              The reason for trying to utilise digital signatures throughout was to retain full authentication of the individual documents. This would be indisputable proof of the origin of the docs.


              I am carrying out my trial with electronic signatures on the documents to be merged then digitally signing the final, completely merged, document.