Brian Jones: Open XML Formats : More on the PDF support in Office: "I know that it is common for folks implementing a format to extend it in order to support whatever extra features that application has. Those of you who are developers know that the way you differentiate your product is to innovate and design new powerful features that deliver value to your customers – it’s good to continue improving. This is not the case though for our PDF support, and we have no intention of ever doing so (even though as far as I can tell there is nothing in the PDF spec that limits third party extensions and Adobe has never tried to stop that until now). We’ve publicly stated that we will not extend the spec, and I’m hoping that as long as we can be clear on that then Adobe will change their mind about wanting us to remove the support."
More on the debate from Microsoft's Brian Jones, responsible for the save-as-pdf feature in Office 2007.