Joining PDFs and changing spacing

[Peter Clark]

        First question: how does one go about joining two PDF files? (I'm running 
Linux).
        Second question: is there an easy way to go from single spacing to double 
spacing in LyX? I've created a fancy layout for my title pages, but when I 
doublespace my reports, the title page also gets doublespaced and looks 
awful. So is there some way to tell LyX to doublespace everything _except_ 
the title page?
        :Peter