Nokia Lumia 520 - Can I open a password protected office document on my Lumia phone?

Windows Phone does not support the password protected office documents at the moment. The password needs to be removed from the document before sending it via email or transferring the file to Skydrive. 

If you would like to see this support added, you can go to the Windows Phone Feature Suggestions website and make requests for future releases.http://windowsphone.uservoice.com.