If you are using the version that came pre-installed with the Surface it is the Click 2 Run version and it uses Application Virtualization and this version uses a Streaming Update, so to force an update, open on of the products and click on the File Tab and select Account and there should be a button that says Update Now....
I uninstalled that version as it is 32bit and I need 64bit for my Data Models....
I uninstalled Office 365 that came pre-loaded and installed 64-bit Office 2013 Professional (from the Microsoft HUP program) and I haven't yet seen an update. Does this version also use Click 2 Run?