Editing a Signed PDF

[Guest]

I know the default answer will be that it stops you by design, the problem is that I'm getting an abnormal result.

I have users in an accounting area that want to edit a pdf to add PO's and other numbers after some initial signatures. I know modifying the text after a signature is a security concern which is why Adobe doesn't allow it. The problem is that one user CAN edit the document for some reason and the other person is asking why.....

When I try to edit the PDF, it gives me the error "This document has been signed and can not be edited". I also get a similar(maybe exact) message from someone else. My version is Adobe Acrobat Standard DC and the other person that has the same error has Adobe Acrobat Pro XI 11.0.12. The person that CAN modify the pdf, despite the signatures has Adobe Acrobat XI 11.0.18.

I do probably need to update the one user's Acrobat but mine is newer and I have been told that editing a PDF after a signature shouldn't be allowed anyways.

Any idea why one person can edit the pdf when they shouldn't?

[Karl Heinz Kremer]

I don't have an explanation why your different Acrobat installations behave differently. It may be due to preference settings.

A signature does not automatically prevent edits: What a signature allows you to do is to verify that a PDF document is identical to the version that was signed. Edits to the document will invalidate the signature. This means that you cannot just look at a document and determine that it was signed, and then assume that the version you are looking at is still the same version that was signed. You will need to verify the signature in order to be certain.

[Guest]

I am a little confused because from all the sources that I've read so far, a signature will prevent modifications. I've seen where it says "This document has been signed and can not be edited" and also where signatures are removed after the modification. Currently I am getting the "can not be edited" error and if I enter CTRL+D and look at the security tab, it says that "Changing the Document: Not Allowed".

My only confusion is how someone can bypass that since I've always at least seen that the signatures are removed(at the very least). I know you will have errors with those signatures even if you were to get to modify it, but since the documents are simple internal PO's, I don't think it would be an issue.

I'm checking preferences but no luck so far.

[Dave__M]

An option that is presented when applying one's digital signature is to lock the document, which prevents further editing.  If a signer chose this option, the document would indeed prohibit edits. BUT, it's an option, not an automatically applied attribute.  It is an acceptable workflow to receive a document, digitally sign it (approving the state of the doc as you see it at that moment), and pass it on for both further edits and signatures.  The state of the document as you signed it is preserved within, even though there were more changes applied.

My best,

Dave

[PatrickK80]

how can this be done?  I am failing to see the option to allow further editing.

[rlpvl]

I don't know about current versions of Acrobat, but Acrobat 10 and earlier allow me to modify a PDF that I've signed. That probably explains why the original poster has one person in their company who can modify a signed document; they must be running an older version of Acrobat. If you validate the signature it will explain that the document has been modified from the original and give you an option to view the originally signed document. I use this functionality regularly, which is one reason I haven't updated.

[Test Screen Name]

Signatures are not a no-edit security. Some software will ignore it anyway. It's more of a reminder. You seem to be very concerned about the possibility of editing but it's detectable and anyone properly trained to work with signatures will know it's been tampered with.

[Julio9807]

There is something wrong with this situation; it may be that a signature is not a no-edit feature, but when you sign a document, a window pops that shows a checkbox for Lock Document After Signing. So, what you expect is to have a locked document (non-editable), when that box is checked. When I do this, whithin our licensed Acrobat XI Pro, the document is locked and it's described as such in the properties; Acrobat can't change it. BUT, recently, a signed and locked document was accesed with PDF X-Change and, except for the signatures, almost everything was editable.

Isn't this a standard pdf feature? Should a "locked" document be edited by other apps?

[try67]

A signed document is still "editable". However, editing it should result in the invalidation of the signature.

If that's not the case then this is a major issue.

[Julio9807]

But then, why provide a lock that doesn't work as expected, one that is only an Acrobat lock?

So, how do you make a signed document non-editable?

[try67]

The word "lock" is not entirely accurate, I agree. It's more of a stamp (not a post-stamp, but a security-stamp). It doesn't prevent someone from accessing the contents and editing them, but it makes it possible to know that it happened.

There's no way to make a PDF document completely uneditable.

[Julio9807]

WOW! Then there's definitely something missing in this business of digitally distributing, working, and signing stuff.

I work at PREPA, Puerto Rico's power utility (government owned), in a dept. where some processess require designs and other documents to be digitally signed for companies and citizens. This was adopted as a way of getting into the digital age, but expecting digitally signed and locked documents to be SECURE; in fact, that was precisely an advertised feature of the digital signature..., authenticity would be guaranteed. Now, it turns out, that what is authenticate is...only the signature? You can't really trust the document.

I understand the validation attribute, but the average person doesn't know about that, and the companies/contractor only want their work to be completed and delivered. In my case, this should mean that, when a project is under construction, designs MUST be checked with the signed documents in our files...; fortunately some of us save copies in PREPA's servers and also require a physical copy to compare and use in the field.

It seems that we'll have to look at our current protocols, because a revision is necessary.

[try67]

But what you're describing is not the workflow of an "average person". If the authenticity of your documents is that important then you have to teach the people in your organization the importance of validating digital signatures, as that's the only way to guarantee it. And yes, you have to carefully study the limitations of any system you adopt... I don't see how using paper documents is any safer, though.

[Julio9807]

As explained, there is our workflow and what the average person/citizen receives.

The importance of validation would imply that legislation may be needed for, say, government regulated design endorsements, for which the use of ONLY one app (Adobe, X-Change, etc.) becomes the sop. Seems to complicated for something that should already be an industry standard. For the average citizen, this should be transparent and trustworthy, sadly, it is not.

Our field inspectors don't use digital documents. The printed design is compared with our digital record to confirm is the same, then it's used in the field.

[try67]

> Now, it turns out, that what is authenticate is...only the signature? 

No, that's not what I said. The authenticity of the signature is the authenticity of the document.

A digital signature keeps a representation of the file within it and compares it to the current version. As long as they are the same it will appear as a valid signature. If they are not the same it will show as an invalidated signature. If the signature is broken it means the file has been altered since it was signed.

[Julio9807]

> A digital signature keeps a representation of the file within it and compares it to the current version.

This implies documents are processed in the same "environment" or company or such. We work with documents that come from the private sector via e-mail or other apps, these are created with whatever the individual has; the only standard is pdf. Almost always, the signature presents a validation issue, but it's no matter to us, because we verify the document as newly received; there is no current version (maybe that's why the issue appears).

What protocol or workflow is suggested when receiving external documents?

[try67]

No, it doesn't imply that. Digital signatures are a part of the file. They are independent of external factors as the application used. However, it's possible to use a non-compliant application and get incorrect results whether a signature is valid or not. To avoid that use Adobe Acrobat or Reader.

[miss_phelps]

I too cannot edit a digitally signed pdf. I want to edit the document and retain the existing signatures and provide for additional signatures. Any ideas?

Thanks.

[try67 · Accepted solution]

As mentioned, that is intentionally so. If you want to be able to edit the file after it is signed then don't use Digital Signatures.

[Test Screen Name]

All editing would completely destroy the digital signature. So I'm not sure what you hope to achieve by continuing and editing.

[I..D]

The only way to be able to edit a signed doc is to "Print" it as "pdf" > open > edit > save.

You will of course lose the digital signature credentials.

Otherwise the whole "Lock after signing" will be useless.

Also, you can have multiple steps of validating and approving a document before it is final and closed.

Cheers

[Erwin231995957ii7]

This is a problem when using a PDF in accounting.  There needs to be a feature that allows for editing in a particular box or field for adding accounting documentation notes.

[try67]

You can use form fields for that. The digital signature field can be set not to lock them when signed.

[woopwoop56284148]

Have a look at Ion5FDD's comment. Open the pdf in your web browser and instead of saving it via 'Save As', go to 'Print'. In the drop-down menu to select a printer there should be an option to 'Save as PDF'. Save it, and that should get rid of the restrictions and allow you to edit the document after being signed.

[try67]

The edited file will not be signed, though. You're in effect creating a new file when you do that.