Can I use the Pentaho Report Designer Engine and its source code to create reports without using the the report designer GUI?

I searched for the answer in this forum, in the Pentaho Ads and tutorials, but did not find anything.

I have a client/server application that offers Pentaho Reports. The user can select some datasources and parameters [like dates] in a super simple HTML Formular. Then these informations shall be sent to the server. The server generates a report based upon the user's input and some fixed parameters [like Layout and CD] and finally exports the PDF Report. This file is then sent to the user in his browser. Voilà. So is that possible?

If it is possible - where can I find a tutorial or help how to?

Thanks and greetings,