According to LiveSide.net, Microsoft Word 2013 will have the ability to edit PDFs. People that use Office 2010 can save documents as PDFs, but are unable to download PDFs and edit them without the use of third party software. When you click File > Open > Browse, you can select any PDF and then open it. It may not be perfect to the original, but the conversion will work best with mostly text-based documents.
Microsoft is also adding PDF viewing capabilities to Word 2013. The first public beta build of Office 2013 is rumored to be built and should be released to the public sometime next week.