I use another printer but wanted to test a solution given here. Using the Script UI Properties that Tom refers to, I was able to create a working AppleScript:
tell application "System Events"
tell application process "Microsoft Word"
tell window 1
tell splitter group 1
tell group 2
tell radio button " Landscape"
---click
if value of attribute "AXValue" is not 1 then perform action "AXPress"
end tell
end tell
end tell
end tell
end tell
end tell
My MS Word version and printer: