If you have make documents using MS Word and you make many formatting changes for the paragraph, fonts, page etc., you will see your file size gets bigger.
Microsoft Word saves files by blocking, so any change you made for your document it will create a new block with the new formatting and disappear the old block without deleting it from the file.
You can solve this problem.
1. If you open your file and select File / Save As and give your file a new name, it will save only the active blocks with out the old ones.
2. If you compare the two files you will see a difference in size.
There is, however, a much easier way.
1. Choose Tools.
2. Options...
3. Open the Save tab.
4. Uncheck Allow Fast Saves.
This makes Word rewrite the entire document file from scratch each time it is saved.
The save command takes slightly longer, but your files can be drastically smaller (especially if you've done lots of formatting changes).