XDA forum member Thunder_ has created an app called Office File Uploader that allows you to move MS Office files directly from your PC to your phone's Office Hub. Using it is easy. Simply extract the ZIP file from the source link below, connect your phone to your PC and double-click the bookloader.exe file. Once connected, go to the Office tab and choose what file you want to add to your device by clicking on the upload arrow icon at the bottom. Make sure your phone is not screen-locked.
Thunder_ discovered that Office File Uploader will also port PDFs over to the Office Hub, which displays them with the red PDF icon that launches Adobe Reader. However, because the Adobe Reader app does not have access to the My Documents folder on the phone it fails to open them.