Open Source Document Management System | OpenKM

Hi,
we are using openkm 6.3 CE. if i want to see the document , touch the file then automatically preview mode will visible.
then i will go the preview section i can able to see the content of the file. if i want to increase it , i can use ctrl + and it is working fine. file is zooming 100% 110%...etc.

but if i click the presentation mode or F11. i can able to see the file. but the thing is ctrl + is not working in prsentation mode.both ctrl + and ctrl - is not working. please tell me why it is not working. if it possible to enable the ctrl + options.
this is the important requirement. if it is possible means, please kindly tell me the way to enable it.please give me the solution as soon as possible.

Thanks.

We are using PDF.js maybe this is a bug in the PDF.js previewer. I suggest check the last version if it happens or not https://mozilla.github.io/pdf.js/