CU Upgrading On Prem Office Web Apps 2013

Problem: I need to upgrade my WCA farm from the RTM version to the March 2013 CU to allow pdf's to be displayed with Office Web Apps.

Steps to upgrade an Existing WCA farm:

1. Copy exe to machine: OWA1 & OWA2 (D:\OfficeWebApps\March 2013 CU)
2. Remove secondary servers from farm.  In my case this is WCA2, remote into SP-WCA2 and run PS> Remove-OfficeWebAppsMachine (on WCA2)
3. Run exe on secondaries (WCA2), Reboot, shut down and snapshot & then on the primary (WCA1)
4. Check primary: verify the url works: http://wcauat.demo.dev/hosting/discovery this can be done on the local machine or using https from a client machine.
5. Create a new OWAFarm, this will run over the top of your exisitng farm   PS> . missing Add-OfficeWebAppsFarm... (on WCA1)
6. Join Secondary to farm    PS> new-officewebappsmachine –machinetojoin “sp-wca1”(Primary)
7. Activate WordPDF PS>  New-SPWopibinding –servername “wcauat.demo.dev” –application “WordPDF” -allowhttp

Perform step 7 on the SharePoint farm.

More Info:

http://technet.microsoft.com/en-us/library/jj966220.aspx

https://blogs.technet.com/b/office_resource_kit/archive/2013/07/24/control-whether-pdfs-open-in-word-web-app-or-the-default-pdf-reader.aspx

You can verify the version of you WCA farm using (not sure this reports the correct version): 
(Invoke-WebRequest https://wcauat.demo.dev
jsonAnonymous/BroadcastPing).Headers["X-OfficeVersion"]

An easier approach is to use Fiddler to monitor the http/https traffic to figure out Office Web Apps farm version:
Open IE
Open Fiddler
In IE, go to the url https://wca.demo.dev/m/met/particiapant.svc, replace "wca.demo.dev" with your Office web apps service url. 
In Fiddler, review the response header, you will see the response header X-OfficeVersion with a version number.