Hi Philipp,
you will find loads of requests to improve OOTB document creation in the ideas-section of this forum. The most recent update we got about this is concerning pdf generation.
https://community.mendix.com/link/space/usability/ideas/1793 but the idea goes way back.
what is your approach ? There are some services. However, I have not used those yet..
https://marketplace.mendix.com/link/component/2026