PDF rendering bug in OS X and iOS
The issue would appear to be the font used for the text, a font called "Corbel"; it is a Windows only font created by MS and included in all version of Windows Vista and above.

Normally, PDF's can be created with embedded fonts, in this case the font is not fully embedded, only a subset (e.g. those characters required for the docuemnt)

Further research shows that there are a lot of issues with Macs reading PDF's created with Word 2007

Note, Chrome includes a copy of those fonts as part of it's PDF rendering engine.