Thank you for your reply.
I've previously noticed that I can change the measurement units in Page Boxes as you indicated in the answer, but it does not solve my problem.
Attached pictures show how apps are showing dimensions!
My English is bad, so I'll try to formulate the same question differently.
I want to configure PDFelement so that always all measures are displayed in the ISO system measure because other systems are not acceptable to me. (I want the application not showing measures in inches rather than millimeters in all places.)
Is it possible to configure the app in this way?