How to decrease file size of exported plots while keeping labels sharp

Question

When exporting rather complicated plots (especially ListDensityPlot) as a PDF or EPS (for publication, for example), the resulting file size can be quite large. For

Answer 1

How about just plotting the function rather than making a list?

plot=DensityPlot[Exp[-(f - f0)^2/25^2], {f0, 500, 700}, {f, 300, 900}, 
 Epilog -> {Thick, Line[{{500, 500}, {700, 700}}]}, PlotPoints -> 50]

Export["test.pdf", plot]

file size 1.1MB