Easy. Simply plug it into your computer and tell iTunes not to sync certain content. You can specifically instruct iTunes when it comes to syncing media with your iDevices. Plug your iPod into your computer and iTunes will come up. iTunes will set the iPod up for you since it is a new device. Then, during the setup process, tell iTunes not to sync audio and video content (there is a specific option for that, you will see it). Then, from the main iPod window within iTunes (where you see a large picture of your iPod), click on the different tabs near the top. There will be one for Info, Apps, Tones, Music, TV Show, Movies, Podcasts, Books (which will handle PDF files, eBooks, and Audiobooks), and Photos. Simply put a check mark next to "Sync..." where the "..." are replaced by whatever media type you want to sync over.
iTunes will work with any number of iPods so you don't have to worry about it getting confused. You could have 230457345 different 2G iPod nanos, 35987398457 different iPad 2's, 345987 iPhone 4S's, 345345 6G iPod nanos, and 3495873957 160GB iPod classics. iTunes would be able to distinguish between each and every one of them without getting confused. You could even sync different media to each iPod if you wanted.
