pdf is a good format but one of it's limitations is when you use fonts that are not common throughout everyone's computer. While someone with just the Acrobat Reader cannot modify a pdf, the format still relys on the font package in the computer of the viewer.

Other than using a common font when making a pdf, or somehow changing what you've created into an actual image (and I don't know if that can be done) you other option is to provide the font in question as a downloadable file for users.