Validate Digital Signature
Validate Signatures
Signature validity is determined by checking the authenticity of the signature’s digital ID certificate status and document integrity. Depending on how you have configured your application, validation may occur automatically.
Set Signature Verification Preference
By default, Foxit PhantomPDF will verify signatures when the document is opened, and will check the certificate revocation status while verifying signatures. If you want to change the setting, please go to File > Preferences > Signature, and uncheck corresponding option in Signing & Verifications group.
Set the Trust Level of a Certificate
The signature of a certified or signed document is valid if you and the signer have a trust relationship. The trust level of the certificate indicates the actions for which you trust the signer.
To set the trust level:
· Choose File > Preferences > Signature.
· Check the option(s) in Windows Integration group to trust all root certificates in the Windows Certificate Store when validating signatures and certified documents.
Tip: You can specify the trust level for a specific certificate in Foxit PhantomPDF Trusted Certificates list while adding and managing the trusted certificate. Please refer to the instruction on Trusted Certificates for more information. If you configure different settings for the same certificate, settings with higher permissions will prevail. Remember that checking trust options may compromise security. Please make sure that you trust all the root certificates before enabling the features.
Check the validity of a signature
By default, Foxit PhantomPDF verifies signatures when the document is opened. An icon appears on the left top of Signature Validation Status message box to indicate the signature status. The signature state appears in the Signature Panel.
The question mark icon 
indicates the signature is not validated.
The check mark icon 
indicates that the signature is valid.
The icon 
indicates that the signature is invalid. The document has been altered or corrupted since the signature was applied.
The caution triangle icon 
indicates the document was modified after signature was added; however, the signature is valid.
The icon 
indicates the signature validity is unknown because the signer’s certificate isn’t in your list of trusted identities.
Check certificate revocation status
By default, Foxit PhantomPDF will check the certificate revocation status while validating a signature if the certificate used to sign a PDF file chains up to a certificate designated as a trusted anchor. Revocation checks are performed based on the revocation information embedded in the digitally signed PDF document, the digital signature, or the Certificate Revocation List (CRL). To view the certificate revocation information, please do the following:
1.Do one of the following:
Choose Protect > Protect group > Trusted Certificates, and double-click the certificate.
In the Digital Signatures panel, right-click the signature, choose Show Signature Properties, and then click Show Certificate.
2.In the Certificate Viewer dialog box, click Revocation tab to view the revocation information, and click Signer Details to get more information on the source of the revocation information.
3.(Optional) If you do not check Require certificate revocation checking to succeed whenever possible during signature verification option in Signature preferences, you can click Check Revocation in the Revocation tab to perform revocation check manually.
Validate a signature
1. Open the PDF containing the signature, do one of the followings:
Choose Protect > Protect > Validate.
Right-click the signature with the Hand command, choose Validate Signature from context menu.
Select the Hand command on the toolbar and click the signature.
Click the Digital Signatures panel, right-click the signature and choose Validate Signature.
2. Pop-up a Signature Validation Status message box which describes the validity of signature.
View signed versions of a digitally signed PDF
A signed version will be automatically saved each time you sign a PDF with a digital signature. If a digitally signed document was modified, you can still view the signed version without the modification. For a document digitally signed several times, you can view each signed version without the changes made after each signature was applied. All signed versions along with their corresponding digital signatures are listed in the Digital Signatures panel.
To view a signed version of a digitally signed PDF, do as the following:
1. Open the signed document with Foxit PhantomPDF.
2. In the Digital Signatures panel in the navigation pane, select and expand a signature, and choose Click to view this version. Or right-click the signature in the document pane with the Hand command and choose View Signed Version from the context menu.
3. Then this version will be opened in a new tab in the application window, with the title of “filename.pdf-Signed Version”. (Note: If the document has not been modified since the selected signature was applied, a prompt appears saying you are already viewing the version covered by the selected signature.)
4. (Optional) Following each signed version in the Digital Signatures panel lists the changes made to the signed version. Clicking on one of the changes will jump to the related area in the document.
Compare versions of a digitally signed document
For a digitally signed document (which might have been signed several times), you can view the differences (if any) between a signed version and the current version you have.
To compare a signed document with the current version, do as the following:
1. Open the current version you have with Foxit PhantomPDF.
2. Right-click the desired signature in the document pane with the Hand command and choose Compare Signed Version to Current Version from the context menu.
3. A PDF document with the comparison result named “Untitled.pdf*” will be automatically created and opened in a new tab within PhantomPDF, and the Compare Results tab appears in the ribbon. The results document arranges pages side by side showing the two versions with the changes marked by different icons and colors. The first page and the second page show a summary and details of the comparison results respectively. See also the help about "Compare PDF Files".
If the document has not been modified since the selected signature was applied, a prompt appears saying you are already viewing the version covered by the selected signature.