Originally posted by jolee1990 i still dont understand what EXIF/IPTC is...
but thank you all for helping
A JPEG file contains two things: it contains image data (the little colored dots that make up your picture) and it contains "metadata" (information *about* your picture, like what camera you used, what shutter speed use used, a copyright message, etc). EXIF is one of the types of metadata that is stored in that JPEG file. When you load an JPEG file into a program designed to display the image data, it shows you the image. Load that same file into a program designed to show you the metadata, and it shows you the EXIF information as well as perhaps other metadata (IPTC is another type; it allows you to store a lot more information about your image).
The software that came with your camera (Pentax Photo Browser) displays both your image and the metadata - the image takes up most of the screen, but the EXIF information is displayed at the bottom. Similarly, Windows Photo Gallery shows you the picture at first, but if you right click an image and select Properties, it shows the metadata. I assume iPhoto offers something similar. Most programs that can display images can also show you the metadata. And most also let you *edit* the metadata to add a copyright message.
So again, your image is *already* protected by copyright law without you're doing a thing, but if you want to take an extra step to help increase your chances of winning money in a lawsuit if someone should ignore the law and steal your image anyhow and then get caught, add a copyright message to the EXIF. Again, many if not most programs that can download images from your camera can also add this automatically, and I recommend of taking advantage of that.
If you want to watermark your image to make it so people wouldn't even *want* to steal your image, then pretty much any program that lets you edit photos should be able to do that. ACDSee, Irfanview, Picasa, Photoshop Elements, etc.