it really depends on what you are doing
corel draw is a vector editing suite, and is great for posters, and large prints- billboards etc. you can also look at adobe illustrator or inkscape- its good for positioning photos in your designs, but not the best when it comes to editing them.
for manipulating photos you need image editing software such as photoshop, paintshop pro, corels photo paint (Iv never used this, so dont know if its any good) or gimp- I personally use photoshop for all my designs- and it is a beast... but is a little expensive.
if you will have a lot of text (think catalogue/brochure/magazine page) you may need to look at something like desktop publishing software- indesign, scribus....
iv given you paid as well as opensource software in the list, so you may want to look at the opensource first until you decide what type of program is going to service you properly.
