When opened on another machine, the formatting is ruined (.docx sent through email)

I work for a tiny ebook publisher. My documents have sophisticated formatting (specific photo locations, tables, headings, table of contents, etc.).

When I deliver tasks to my employer in.docx format, he examines the file and finds it absolutely disorganized. Photos and text have been rearranged. Headings are not integrated any more. Text overflows into new pages.

I can't just convert it to.pdf because of constraints at work (although that file type does preserve my formatting). What can I do to ensure that my employer can access my files with flawless formatting?

Extra information: we both use Gmail, all fonts are standard, and we both use Word 2016. I am a PC user, while my employer is a Mac user.


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