Need help with troubleshooting MS Word document sentence jumping

[SHZR]

I am having issues with the word formatting for MS Office Word system. Apparently once I have typed the document and sent it to the recipient, once he or she tries to edit it or add additional information to it the lines and word formatting skips around the line instead of just beginning at the next space. My OS is Windows 7. Theirs is Windows 2003-2004. I have saved my documents to them as compatibility mode for Word 2003-2004 however this seems to be happening recently. What is the problem here and can I easily fix this and prevent it from happening again?