How can I know that a document hasn't been modified after signing?
Updated
When a document has been signed by all parties, the document is locked and provided with a digital fingerprint at the bottom of each page, as well as a receipt page (last in order on each signed case).
Learn more about how to verify a signed document.
You can also find instructions on how to verify documents on the Receipt Page, which you can find last in order on each signed case.