PDF: Timestamp X.509 certificate signature when signing document
First load the document as described in the corresponding how-to article.
To timestamp the document signature using X.509 certificates you need to use TSPClient property of TElPDFPublicKeySecurityHandler component and one of TElFileTSPClient or TElHTTPTSPClient classes, which will perform the timstamping.
The timestamp request is created automatically by TElPDFPublicKeySecurityHandler when the signing is performed. All you have to do is create an event handler for TElFileTSPClient.OnTimestampNeeded, if you want to use custom timestamp processing or set TElHTTPTSPClient.URL property if you want to use HTTP(S) transport. Also you need to assign the transport (an instance of TElHTTPSClient) to HTTPClient property of TElHTTPSClient class. If you need to setup connection properties (such as username/password), do this via an instance of TElHTTPSClient.