Re: now it's all Zeros when I open it
Those are not Zeros.
Those are "missing character" placeholders, the PDF reader is unable to render them (given what characters they are, and the font specified vs. what's available on the device) so it renders a generic "blob" just to let you know that "there was supposed to be a character here".
And yes, @Paris Geek is completely right -- Aqua's job ends at fetching the attachment and opening it in whatever app says it can handle it.
The app does not rewrite PDF's on the fly, does not add red eye effects to photos, does not delete files from .zip archives, etc.
