From Adobe Systems:
Adobe Acrobat Reader for Pocket PC extends the value of Adobe Portable Document Format (PDF) files beyond desktop computers to handheld devices running Pocket PC software. Acrobat Reader for Pocket PC allows you to choose two ways to view Adobe PDF files. One allows you to view the Adobe PDF file exactly as intended. The second utilizes tagged Adobe PDF files, which provide the best reading experience on handheld devices because text and images can be easily reflowed to fit the screen size. Tagged Adobe PDF files can be created with Adobe Acrobat 5.0, Adobe PageMaker 7.0, or Adobe InDesign 2.0.