Clear Signature Functionality

Are you sure others are able to clear your signature? The only people that should be able to do that are those with your signing certificate (Digital ID). A test of this is to open the Security Setting dialog (Advanced Menu), expand Digital IDs (on the left side of dialog), then click on Digital ID Files. You should see a list of all of your Digital IDs. Select the one you used to sign the file and click on the Detach File item at the top of the dialog window. This will disassociate that Digital ID from Acrobat. Now open the file in question and try clearing the signature. You should now be unable to clear it.

More information may be needed. There are other vendor products that can process PDF's but do not comply with Acrobat's security standard.

What product the is the other user using?

What method are you using for the signature security?

Does the other user have your cirtificate and your password?

Having a second signture added to a PDF will invalidate the first signature, as the second signature field has changed and thus the PDF has changed.

An important point to consider is your application. Suppose someone is able to clear your signature one way or another. If they then fill in data in a form, it is not siged by you. But then suppose they couldn't clear your signature. What prevents someone from obtaining a blank form and filling it in and arriving at the same point?

There are two issues: protection of data and authenticity of the data. Since with most PDF forms, the physical file is sent and it is always possible for an attacker to create a look-alike form. The application must determine the authenticity of the data in some way such as a valid digital signature from a trusted party. Protecting data in a document so that it can't be changed is never a substitute because it depends on an attacker using only a trusted application that follows the protection rules, something an attacker is not likely to do! The attacker can always change the data, but cannot forge the signature on it.

Hi,

I tried sending a signed form to a user using adobe reader 9, the user was not able to clear the signature. However, for user using lower versions, they can easily clear the signature. Is there any way we could only allow the clear signature for the original author of the form?