Failed to download as PDF in OM 5.0.0-M3

[Pin Lv]

Hello,
  I install openmeeting 5.0.0-M3 on Ubuntu 18.04 LTS following the guide on
openmeeting website.
  But when I want to download the whiteboard to pdf, it told me The
connection to the server has been lost. my file is about 154Kb
  I did some research, it told me I need to change the maxPostSize
in jee-container.xml.
  But I cannot find this file in OM5.
  where can I change to allow me download as pdf?
Best Regards,
Pin