Well you could render at a lower resolution and then blow it up to a larger size, but you're losing detail that way and making things pixelated or fuzzy. (Not exactly great for print.) If you want a nice sharp and crisp image, render at or slightly higher than the dot pitch being printed. Of course how much this matters also depends on intended viewing distance. You could probably get away with 72dpi for something like a poster to be viewed from 10ft away, but that'd look cruddy if it was at that resolution for a picture in a magazine page 1/4 the size because now it's viewed at less than arm's length.

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Barbequed Pixels?

Your friendly neighborhood Wings3D nut.
Also feel free to browse my freebies at ShareCG.
There might be something worth downloading.