The document author can certify their own PDF documents. The author can specify what changes can be made to the file after certifying.

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.

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.

Many business or other practical applications need digitally-signed documents to be verifiable for months or years after signing. To reduce chances for error or fraud, Long Term Validation (LTV) is introduced for digital signatures in PDFs.

Validate a signature by selecting it through any available method (Protect > Validate, right‑clicking, or using the Digital Signatures panel). A Signature Validation Status message box then appears, showing the result.

By default, Foxit PDF Editor 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.

By default, Foxit PDF Editor verifies signatures when the document is opened. The signature state appears in the Signature Panel.

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.

Foxit PDF Editor automatically verifies signatures and checks certificate revocation when a document opens. To change this behavior, go to File > Preferences > Signature, and then uncheck the relevant option in the Signing & Verifications group.

This section includes details on how to modify or delete a digital signature after signing the document in Foxit PDF Editor.