PDFs load a translucent image of my desktop, not the PDF itself.
When I try to open a PDF in Firefox 4 (up to date), the PDF loads as a partially translucent image of my desktop background (or whatever program is open behind Firefox) and it renders the PDF unreadable. I have to download any PDF I want to view because the PDF, as well as the Save/Print/etc. buttons are glossy and nearly impossible to see.
Opaite Mbohovái (1)
uninstall adobe PDF reader from your computer and then restart your system. after restart install it again.
or try the free the replacement of adobe PDF reader;