Margins change between desktop and mobile

I have taken a while to carefully sculpt an important document on desktop (my resume in fact). It took me a long time to squeeze it all onto 2 pages, adjusting the top and bottom margins, fonts, etc, to make it happen.

The strange thing is that when I look at the document on Office for Mobile (Android, Nexus 4 phone, Android 5.1.1), it overflows onto a third page and the margins look wrong, as if they are the default setting. When I save as a new document, the changes ae kept in the new document without me doing anything to insert them.

What I'm worrying about, apart from the fact that their is a format change between devices, is that if I open a document on mobile which made on desktop and then share it, I will be sending an unfaithful copy. Furthermore, it will definitely cause problems when people collaborate.

Having taken a couple of minutes to check before posting, I noticed that the new document saved on Android actually had a header inserted (I don't know why that would happen). When I remove the header, the document is now on 2 pages, but there has been a slight change (line 1 of page 2 has moved up to the bottom of page 1). I've checked - you can remove headers in Word for Android (painful but possible) but it has the same line-shift as I found on desktop.

Please, does anyone know how I can avoid Word for Android changing my document?