I use Acrobat X Pro, Windows XP. What do you use?
I have used Photoshop to test the exact colours in screen shots, since comparing appearances is tricky. I see the same colour values in my Acrobat that you see in your Word. I have the same colour settings as you (without the Creative Suite synchronization stuff).
No CMYK conversion has taken place. There is no profile attached to this image, so the colour is really almost irrelevant. How it looks is going to vary enormously according to the software in use and people's default settings, even on calibrated monitors. Maybe actually applying a profile would narrow the differences.
I downloaded the files and except for compression artifacts in the pdf flower pattern, they appear to be the same color.
Two possible places to check: Word's PDF preferences next to the Create PDF button. If you use Standard, the color profile is sRGB. If you picked a Press Quality setting, the sRGB file is converted to CMYK. You have to click Advanced Settings under the Standard or Press Quality, then click Color in the left pane to see what the Color settings are.
The other culprit could be Windows 7 Color Management. (found in the Control Panel) That's about all I can think of. If neither works, I'll have to defer to better minds.