Word 2010 cannot automate PDFs on its own. At the very least you'd need to employ Adobe Acrobat Pro for this. As for working with a scanned image, that might be possible but the scan would need to be:
• an image of the page (i.e. not using OCR)
• resized to exactly the same scale as the original; and
• overlaid with a table and/or textboxes so that the table cells/textboxes are positions over the input fields on the image. In other words, a lot of effort to avoid filling in the PDF.

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]