For people who don't have the font on their system, embedded fonts work fine for viewing the PDF in e.g., Adobe Acrobat or Reader, but not for opening it up in Corel or Illustrator for editing. Not all fonts allow embedding either. I have a font that I created from letter-shaped vector objects in Illustrator (and then using Fontographer to create the font from them), and ironically, Illustrator won't let me embed that font in a PDF. It says:
"The font EMC1986 could not be embedded in the PDF document because of licensing restrictions. Stroked text will not be visible."
Apparently, unless you specifically allow embedding when you create the font, it defaults to not being allowed, and I never found the option in Fontographer (assuming there is one) to allow embedding, though I didn't spend much time trying to find it.
On the other hand, Corel (12) will embed that same font into a PDF, no questions asked. However, Corel doesn't get along with that font very well (Illustrator has no issues with it at all), i.e., if I type a word, it appears to be working fine, but when I am done typing and deselect the text, the first letter I typed disappears or is replaced with a rectangular outline. It is bizarre. As a workaround, I can make the first "letter" a space, which works most of the time. It is strangely inconsistent with regard to what it does to that first letter and which workarounds will actually work.
I generally convert text to vector objects as well in my final files, just to be on the safe side.