problem is, that it doesn't work on my local server (wamp) either, and it has set access via HTTP. I'll try ask our ICT for enabling access via HTTP for more testing.
Edit: So we changed protocol to unsecure HTTP, but problem with PDF is stil there. I actually made a pure fresh installation from git release omp-1_1_0-0 on my local server and PDFs still doesn't display.
Thank you very much for your help