That's not correct. But it may be that Acrobat doesn't support the DigitalSignature tag. ... View more

If YOU are the signer, you should be able to delete the digital signature, UNLESS you have locked the document. The (deleted) signature is still in the document, in an earlier version, but should show as deleted in the signature panel. (There is a special consideration if you are deleting the last signature on a document) You can't really just roll the document back to an earlier state, especially if you are the first signer (since there is no earlier state revision of the document). When a PDF is modified, the modifications are saved by appending the revision information (version) to the original document. There are no regular modification procedures that roll the document to an earlier state. An exception to this rule is when there are (some) digital signatures on the document. You can save a version that corresponds to a particular signed version, with all the subsequent signatures (and form fillout, etc) removed. That option is available from the signature panel. ... View more

Last time I looked, PDFs exported from Adobe Sign are password protected with an Owner password only. The User password is null, so you can view the document. The Owner password does restrict some operations. ... View more

For a signature to be trusted by a third party, it must be signed by a certificate that has been issued by a trusted provider. I think you will need to obtain a commercial certificate from one of the Acrobat trusted providers. ... View more

For the purposes of "Doc Mod Analysis" (part of signature validation), metadata is considered to be external to the PDF, and not checked for changes. ... View more

Metadata is considered to be external to the PDF. ... View more

Yes, but that's not why you can't encrypt after signing. Initial encryption requires a Full Save, and that would break any digital signature. The digital signature after encryption adds an encrypted incremental save section. On an initial Save and Sign, the encryption is applied during the signing process. ... View more

A digital signature captures the hash of all of the bytes in the file. If you encrypt a file, those bytes will change. You can encrypt first, then sign. ... View more

Unfortunately, this is an n^2 process (validating signature 37 requires validating signature 36, etc). Enabling LTV will keep Acrobat from having to go on-line to retrieve revocation information. That might help. ... View more

You don't say what country you are in. Each country has their own idea of digital signatures, document signing, data retention, etc. You should get someone who knows the local rules to help. Perhaps the IT department of one of your correspondent banks. ... View more

Unfortunately, error messages from Acrobat are not entirely descriptive. You will need to make a formal bug report, and include a screen shot of the error message with "details" expanded. ... View more

The key usage of the OCSP signing certificate is: Digital Signature, Non-Repudiation (c0). The extended key usage is: OCSP Signing (1.3.6.1.5.5.7.3.9). The key usage of the root certificate is: Certificate Signing, Off-line CRL Signing, CRL Signing (06). But there is no extended key usage for OCSP signing in the root certificate. ... View more

The most likely explanation is that the document was digitally signed by a non-Acrobat application, and the SigFlags entry in the AcroForms dictionary in the document Catalog was not set properly. ... View more

Use Adobe Sign. Documents may be sent in parallel to all recipients, and the signatures collected when each recipient signs. The final document you receive will have all signatures. If you just mail to multiple recipients, you will get 'n' copies back, each with one signature. ... View more

No need to hack the code, the password algorithms are part of the PDF standard, for all to see. Having said that: Acrobat 5 compatible passwords (40-bit RC4 encryption) can be bypassed because 40-bits is small enough to generate a table of all possible keys (called a Rainbow table). You can't crack the password, but you can crack the file. Acrobat 6 introduced 128-bit RC4 encryption. Acrobat 7 has 128-bit AES encryption. In both of these cases, Rainbow tables are not practical, but the password is limited to 32 characters, ASCII. Short, plain, passwords are hacked using a dictionary attack: a file of thousands of common  passwords is tried, followed by exhaustive search over all passwords. Up to about 6 or 8 characters, a password can be found in at most a couple of days. So if you use one of these encryption methods you should use long (12 or more characters) pass phrases (yes, spaces are allowed). Acrobat X takes it one step farther, using 256 bit keys and AES encryption, and allowing very long pass phrases (up to 127 characters) in any language. In addition, the Acrobat X password algorithm was deliberately designed to run slowly, so it takes a long time to do a brute-force search. You still want to stay away from dictionary attacks, though. ... View more

Digital signatures can only have a single appearance, so you can't sign once and make the signature appear on all pages. Non-digital signatures (stamps, scribble, etc.) can have multiple appearances, so you can have the same signature appear multiple times. ... View more

Next, read RFC 5126 CMS Advanced Electronic Signatures (CAdES) ... View more

The CRL in the cache has expired (July 15, 2017). CRLs are cached when downloaded, and that requires that you be connected to the internet. Since CRLs are issuer specific, there is no preemptive caching. They are only downloaded when needed. You need to be connected to the internet when validating a signature for this to happen. ... View more

That won't work, of course, since there is no way to specify the Owner password in the Action. ... View more

The certificate should be the same, but maybe it got lost when you switched. Check Edit->Preferences->Signatures->Identities & Trusted Certificates. ... View more

If this is a digital signature, you must have the same certificate that was used to sign originally. You can't delete a signature signed by someone else. ... View more

You need to login to the password certificate first, so that it can be seen. Preferences->Signatures->Digital IDs. ... View more

This is a Security Settings option: Passwords and password time-outs can only be set for PKCS#12 IDs. Since a file can contain multiple IDs, passwords and time-outs are configured at the file level rather than for individual IDs. Note:If the is read only, then the Change Password and Password Timeout options are disabled. To change the password timeout: 1. Choose Advanced (Acrobat) or Document (Reader) > Security Settings. 2. Highlight Digital ID Files in the left-hand tree (Figure 13). 3. Select a file in the right-hand panel (Figure 13). 4. Choose Password Timeout. Tip: The password timeout feature interacts with the Login/Logout feature as described in “Logging in to PKCS#12 Files” 5. Configure the Password Timeout Policy dialog by specifying when a password prompt should appear: Always: A password is always required each time the digital ID is used regardless of whether or not you are logged in to a file. After: Choose a value from the drop-down list to set a time frame. Once per session: A password is asked for only once while the application is open. Never: The password is not usually required when using this ID and you are logged into the file. 6. Enter the password. 7. Choose OK. ... View more

Datalogics ( http://www.datalogics.com/products/pdf/pdfjavatoolkit/ ) sells the PDF Java Toolkit developed by Adobe. It can handle digital signature creation directly. ... View more

That's the most likely answer. The file shows the Author or Creator as "Merge Report", with a comment: "Created by Wnv/EP PDF Tools". It also claims compatibility with PDF-1.4, which is a very old (Acrobat 5.0) version. I can see no reason for a SigFlags entry, at all. ... View more

This document has no signatures, BUT it has an AcroForm dictionary with a SigFlags entry of 2 (which means "Append Only"). I would not be surprised to discover that Acrobat is taking the existance of the SigFlags entry to mean that the document is signed, which it isn't (if it were, the SigFlags value would be 1 or 3). Possibly (probably) a bug in Acrobat. I don't know why there was a SigFlags entry in the first place. It is optional. That may be where the real problem lies. Did you change the file creator lately? After writing the above, it occurs to me that the SigFlags entry of 2 would prevent a Full Save of the document. Encryption requires a Full Save (no incremental save sections). So the dialog didn't give the correct reason, but you can't change the security settings if you can't Full Save. Again, you need to check how the file was created (and modified, since there are several incremental save sections) ... View more