A quick tip here to explain how .CAB files work with the Microsoft Help Viewer Output. CAB files are signed files and just like any other signed file and you can use your own tooling to sign or re-sign them.
If you wish to manually sign your CAB file using another tool, you will need to ensure that you enable signing and have a certificate (a dummy or self singed certificate will do) in order for Document! X to generate the .CAB during build. You can identify your certificate details in Options (Microsoft Help Viewer Signing page). You can then enable signed .CAB output on the Compiled Help page in the Build Profile Editor.
Once the signed .CAB is generated, you can then use another tool (such as Advanced Installer) to sign the .CAB manually with your actual certificate.