If you print directly from Pages the Mac will work most things out and you get a better result, not perfect but better.
An inkjet printer actually spits at an enormous number of extremely tiny drops to make up the picture on the page. The way it does it is not the same as a commercial print job and therefore low resolution is not so apparent. The tiny droplets also tend to soak into the paper and merge giving a smoother appearance.
If your text overlaps transparent objects it can be rendered at low resolution too.
I suspect your text is not black ink, but a mix of CMYK the process colors which have a half-tone dot pattern put on them to make the specific color, this can look fuzzy when printed commercially.
http://en.wikipedia.org/wiki/CMYK_color_model
Despite what everyone likes to tell you, printing a quality job commercailly is still technical and that is what designers are trained to do, as well as actually think about layout and design.
Peter