So what exactly is Metro, and why does it have so many folks worried about the future of PDF? In essence, Metro is:
A ZIP container file. These are now very familiar to Windows users, and can be handled easily by Windows applications. ZIP archives act as compressed containers, aggregating text, images and other elements into a single file.
Self-contained. Like PDFs, Metro files can be self-contained, meaning that it includes all color information, fonts and other supporting files required to render the document.
A print format. As such, Metro uses XML to describe a page description language. That means that it's similar to other PDL's like PostScript, describing where characters, words and images need to be placed on the page.
An XML-based document display format. Like PDF documents, Metro files can be viewed reliably on any machine that supports the format.
Windows' antiquated graphic device interface (GDI) print subsystem has long been due for an update, and WinFX will incorporate a new print subsystem to go along with Metro. Perhaps ironically, the new subsystem will benefit creators of PDF as well. Currently, documents "printed" to PDF are sent through the GDI print subsystem. A PDF print driver then either converts this GDI output directly to PDF, or to PostScript, which is ultimately turned into a PDF by a translation program such as Adobe's Acrobat Distiller. There are also features supported in PDF that will be lost in translation if the PDFs are created in this way. For instance, transparency is supported by both PDF and Windows applications such as PowerPoint 2003, but that information will still be lost if the document is printed to PDF using the current Windows printing route.
OK, so you want to stamp your document. Maybe you need to give reviewers some advice about the document's status or sensitivity. This tip from author Ted Padova demonstrates how to add stamps with the Stamp Tool along with related comments.