Se o espaço não for um grande problema, basta economizar na mais alta qualidade que você precisará imprimir. A redução da resolução é muito mais fácil do que o upsampling.
Printer settings of 360dpi, 720dpi, 1440dpi and 2880dpi are often found. However the difference between then is subtle at best. Most people probably couldn't tell the difference and 360dpi usually looks great. Changing DPI does not change the size of the print. ppi controls that. dpi controls print quality (though as I said, over 360dpi you typically don't see much change).