I want to add a font to Photoshop CS5. The font name is Futura Medium. I can purchase this font at Fonts.com Will I be able to add this to CS5
As Mike states, fonts are installed at the system level, in most cases (very few exceptions to this).
The only question will be whether the fonts.com Futura will display and function properly in Photoshop. Adobe programs, and especially Photoshop (and PrPro's Titler), are very sensitive to the exact fonts. Some are just not well-written (do not know that one), and will not function, or display. My guess would be that, when installed, PS will see it, and be able to use it perfectly.