Liz,
Photoshop is virtually the same on Mac and PC -- I've taught university courses on both platforms in the same classroom.
Stormo is correct about images coming in from digital cameras as 72 dpi, but what you have to do is set your camera for the largest possible number of pixels. If the image has enough overall pixels, you can trade resolution for physical size. Open Image Size. Where it says 72 dpi, type in 300 and watch the physical dimensions of the image shrink. If you do not have enough total pixels, creating a higher resolution image will make it extremely small in dimension.
While you *can* enlarge a digital image, you will drastically reduce the quality.
Also -- DO NOT resave your image as a jpeg, as this is a lossy format and your quality will degrade. Once you open it, save it as a Photoshop file or a TIFF. Then, when you're done, you can save the final version as a jpeg if you like (but save it also as a Photoshop file).
If you are getting your images from someone else, ask for the original image with ABSOLUTELY nothing done to it. There are so many bad things that can be done to electronic images that cannot be fixed.
If you want to do quality work for print, I recommend taking a class at the community college, as there are many, many things involved in producing printworthy images. It is far different from producing images for web. Not only dpi, but black point, white point, dot gain, gamma...and little things like using unsharp mask rather than sharpen or sharpen more, or using levels rather than other means of adjusting your greyscale.
There are some very good online tutorials, but you almost have to know what you don't know to take full advantage. You can also get some excellent books in Powell's technical book department.
Then, after you've taken a class and/or read the books, make friends with the person doing the imagesetting at your print shop. They can best tell you what is right for their press. Many supposedly pro designers think they know more and lose out on a lot of expertise.
You also have to consider what page layout program you will use, as documents are rarely done entirely in Photoshop, as it is not really designed for setting large blocks of text or multiple pages. Industry standards for page layout programs are Quark and InDesign, both of which are available on both Mac and PC. Word is NOT considered a professional page layout program -- it's only good for driving graphic designers insane when they have to undo all of the formatting originally done, lol.
All have a rather steep learning curve, yet each is worth its weight in gold, and then some.
Sorry for taking such a shotgun approach -- it is late afternoon, after all!
Feel free to call or email with any questions.
