The Acrobat PDF format is essentially a sealed file format, so making changes should only be undertaken on as minor level as possible; and indeed is possible within Acrobat Professional as long as you have the correct fonts loaded that exactly match those that are used in the Acrobat file. The text mark-up tool can be used to edit text for example, after which you can re-save the PDF file with the necessary changes.
Using MS Word is not the way to edit a PDF, however if you need to place the PDF in Word to act as a page template in the background for example; this is infinitely more successful on a Mac (it would appear) than it is on a PC. This is because the Mac (running 2008 Word) handles PDFs in a different way to the PC (running 2010 Word). In the Mac version, the insert-picture-from file command will place the original PDF unchanged on the page - to be resized as necessary, with no loss in quality when printed or re-saved as a new PDF.
Unfortunately, it appears that the PC version of Word converts the PDF file to an image file as it is importing the PDF, thereby changing it to an image format that is inferior in quality when either viewed, re-saved as a PDF or printed as hard copy.
Unsure as to why the same program treats the same file differently on different platforms... but there you have it. Hope this helps.
