Office 2011(mavericks). Attachments from outlook only open word & excel as read only
This is a feature of Office 2011 Outlook.  The behaviour is not limited to Mavericks or Word or Excel files.

When you double click an attachment to open it, a copy is saved under your Library folder (in ~/Library/Caches/TemporaryItems/Outlook Temp).  This folder is not generally visible or intended to be accessible to users hence the "Read Only" attribute of the file. 

You can either


double-click the attachment in Outlook (to Open it in its default application) and then Save As... to, for example, your Documents folder before editing or
right-click and Save As... in Outlook itself, in which case the file will not be "read only".