I am a Lyx user on Windows 7 64 bit using Lyx 2.0.7. Whenever I view PDF I find that Adobe Reader defaults to always being on top. This can be an issue as it means if I would like it to compile the PDF in the background, I constantly have to dismiss the PDF window as it pops up several times depending on what stage of the compile it is in. This seems to occur for both pdflatex and luatex.
I also use Lyx on RHEL6 (linux) and do not have this issue on this operating system. Is there a way to get lyx to load Adobe Reader in the background, rather than 'on top' of other windows? -Ben