Just look at the numbers. A ten megapixel camera such as the K10D gives an image with 3872 pixels on its longer side.
if this is printed at 300 pixels to the inch it gives an image 3872/300 = 12.9 inches wide.

Most good quality printers can print at 1440 or even 2880 dots per inch, so the printer is using 2880/300 = 96 dots of ink per pixel.

I think the printer is more than capable of rendering an image from a 15 megapixel camera without any problem.