Can you help me understand Adobe Document Digital Signatures and how it works with NetWeaver ?

HI

I am trying to understand SSO with the Adobe Document Digital Signatures in NetWeaver AS ABAP (WebDynpro) - as described at Digital Signatures in Form Integration - Web Dynpro for ABAP - SAP Library

I assume (might be wrong) that the user first logs onto the Web Dynpro ABAP application using a web browser, and so the authentication of the user is handled by the ABAP ICF engine. Once the SAP user id is known, is this SAP user id used for signing Adobe documents ? What is Java stack used for in this case, if anything ? If client side certificates are used, does NetWeaver launch Adobe Acrobat on users workstation, and if so, which user id is used to sign the document ?

Thanks

Tim