Say you're like me and you make some flyers or something with the idea that you can print them into PDF files using Adobe Distiller, take them down to Kinko's and have somebody in a blue apron output them directly on one of those newfangled PDF-reading copy machines. Unfortunately Distiller refuses to embed the free TrueType fonts you got off of some web site because the font authors decided that embedding is forbidden (or the font creation software they used was set to 'evil'). You're faced with either redoing the document using different fonts or trying some non-PDF format which will require computer use fees at Kinkos and has the added bonus of possibly not outputting correctly. If you're like me, you're pissed.
Ever since Acrobat 4, Adobe has decided to crack down on the terrible scourge of TrueType (PostScript Type 1 isn't affected) font piracy by having Distiller and PDF Writer police the licensing bit which is a part of the metadata on each font. What's that you say? If you were going to pirate fonts you would download them from usenet instead of trying to tear them out of PDF files like some homeless guy scrounging around in a dumpster? Me too, but apparently the TrueType font creators union has a lot of pull inside Adobe because their desires were put even before those of the service bureaus (http://www.pdfzone.com/rich/fonts1.html) for whom daily life has been made much more difficult by this poorly documented "feature".
The bit in the fonts that controls this Distiller behavior is known as "fsType" in Macromedia's Fontographer, "Font embedding level" in Microsoft's Font Properties Editor, "Font embedding - Licensing rights" in High Logic's Font Creator Program and "a massive pain in the ass" by myself. If this bit is not specifically set to allow embedding Distiller will refuse to embed the font. After some trial and error with Fontographer (which is not the tool for this job) I discovered that the aforementioned oh-so-creatively named Font Creation Program (see http://www.high-logic.com) should work well. Open a font (or drag and drop several to the folder icon on the toolbar) and click Format -> Settings -> General -> Edit. Then uncheck "Restricted License embedding" (or whatever is checked). Now check "Preview & Print embedding" and "Editable embedding" (just for good measure). Hit save and you're on your way to sweet, delicious PDF goodness.
Of course I haven't actually done this because it's terribly illegal in the U.S. under the DMCA so unless you're ready to become an outlaw (or your local laws are more accommodating than mine) I suggest you don't either.
Update: Another (much simpler) way to accomplish this is by using the embed utility.