Insert PDF image in MS Word
It isn't possible to insert PDF files into Word documents (I haven't tried Word 2010 yet, so I don't know if this has changed in Word 2010).
The only way to insert vector images into a Word document is by using the EPS (encapsulated postscript) file format.
Converting a PDF to EPS
Adobe Illustrator
Open the PDF file in Illustrator and save it as an EPS file.
Adobe Acrobat Professional
Open the PDF file in Acrobat Pro and then Export it to EPS
File > Export > Postscript > Encapsulated Postscript
Inkscape (Open source vector graphics program)
Open the PDF file in Inkscape and save it as an EPS file.