PDF with miscellaneous Unicode symbols, including the planets and the signs:
http://unicode.org/charts/PDF/U2600.pdf
The good thing with Unicode is that you can use astrological glyphs without having access to an astrological font. The bad thing is that if you post it online and the reader has an old Windows system, their computer cannot read all glyphs. (Jupiter especially seems to be a problem.)
However, for inclusion in PDF-files they work great, and it is easier than working with images.
And on this page you can learn character input, if that is new to you:
http://en.wikipedia.org/wiki/Unicode_input