A family of Microsoft word processing software products for creating web, email, and print documents.
Short answer is that you cannot prevent this.
You can minimize it.
This goes to the nature of Word and has been true as long as Word has been around. Word uses local resources in formatting and generally will be different on different machines.
Here are two articles that explain this and have tips that can help you minimize the changes.
- Why has my page layout changed when I open my document on a different machine? by Suzanne Barnhill, MVP
- What happens when I send my document to someone else? Will Word mess up my formatting?
You can convert to pdf on your machine and send the pdf.