How do I save files locally using Microsoft Office Mobile for Android?

I'm agree with Mr. Zaid Mahadin

The easiest (possibly the only) way I found is using OneDrive from the Play Store.

1. Open the document using Microsoft Office. Tap Save as from the options menu.

2. Save it to your OneDrive (only option as of now)

3. Select Open in OneDrive.

4. On OneDrive, tap the Download option.

5. Select the folder you want to save the file in (within the Downloads folder).

6. Use a filemanager (such as: ES File Explorer File Manager from the Play Store).

1.Open the document you already prepared using microsoft office and pick the "save as" option

2. Save it in your onedrive or in your device storage

you can save it on your smartphone or you can save it using onedrive a cloud storage as long you use a outlook email.. just like Mr.  Zaid Mahadin answered :-)