How to convert signed documents to PDF/A?

I often get the question whether it is possible to convert digitally signed documents to PDF/A. Because there's no short answer to this I thought it would be helpful to explore the topic a bit into more detail.

What technical means does PDF offer to perform such a conversion?

Generally spoken, the conversion of a PDF document to a PDF/A document is done by deleting and updating existing objects and adding new objects. Theoretically, this could be performed by using the incremental update mechanism of PDF which would not break the existing digital signature. Practically, however, the most important viewer, Acrobat Reader, only accepts very limited updates, such as adding comments, once a document is digitally signed. Thus, the incremental update feature cannot be used for this purpose and, unfortunately, there is no other suitable mechanism.

But how can the problem be solved then?

There are several possibilities. A simple solution would be to convert the document to a PDF/A-3 file and attach the original file to it. However, in some archiving environments, PDF/A-3 is not permitted. In these cases the conversion tool can create a page containing the verification protocol of the digital signature, convert the original file without the signature to a PDF/A file, merge both files and resign the result.

How would you solve the problem in your environment? Please let me know and post a comment.

11 comments :

  1. I should say convert the signed PDF to PDF/A-2, create a page containing the verification protocol of the digital signature, merge this page with the new PDF/a-2, bring this document in an PDF/a-2 envelope and sign this envelope.

    ReplyDelete
    Replies
    1. Cool! Thank you for your creative contribution.

      Delete
  2. This comment has been removed by a blog administrator.

    ReplyDelete
    Replies
    1. Hi - Our policy doesn't allow advertising and we've to remove your input.

      Delete
  3. This comment has been removed by a blog administrator.

    ReplyDelete
    Replies
    1. Dear John
      Thanks a lot for your comment.

      You wrote:
      Thank you for the article.
      We are facing constant growing of data amount in both the Web and personal computers including PDFs and other office-related files that may be valuable. The more information we need to proceed the more time it takes.

      Unfortunately our policy doesn't allow for advertising.

      Delete
  4. This comment has been removed by the author.

    ReplyDelete
  5. This comment has been removed by a blog administrator.

    ReplyDelete
    Replies
    1. Dear ShawnM
      Thank you for your comment but our policy doesn't allow advertising and we've to remove your input.

      Your wrote:Thank you for the good advice.
      The way you described here really works well and I find it the easiest I've ever tryied before. Since my company's documentation has started being processed by [...] I didn't have any troubles.

      Delete