For absolute certainty—though with loss of text searchability and quality at extreme zooms—rasterize the PDF to high-resolution TIFF or PNG. This replaces all text with pixels, making font substitution impossible. Do this only for final, uneditable distribution.
Free Adobe Reader does not allow you to embed fonts. However, you can try this: Download Font Substitution Will Occur
While the phrase is standard to Adobe, other applications use similar language. Download Font Substitution Will Occur
: Double-click the font file and click Install Font in Font Book. Download Font Substitution Will Occur