1:

Open two documents in Adobe Acrobat.
Then select “Windows” and then in the pop-up menu click on “Tile” and then in
the next pop-up window click on “Across Monitors”.
This can be very handy if you want to view both the drawings and specification
at the same time on a full size screen view. In order to do that though you
will need to make a duplicate of the application (or whatever PDF document you
are looking at). To make a quick copy or duplicate of the document you are
looking at just click on “Window” and then in the pop-up menu click on “New
Window”.

2:
Click on “Start” then “Run”. In box, type “acrobat /n”. This will
open another instance of acrobat in which you can open either another file or
the same file you have open in the other instance. You can do this multiple
times to have multiple instances of the program running. Then you can just move
one instance to one monitor and the other instance to the other monitor. Each
instance can be closed independently from the other. The only limitation with
this is that if you have the same file open in both instances of the program,
you cannot save either with the same file name.

3:

Add the “/n” to the Target in the Adobe ICON on the Desktop or any shortcut to
it. i.e Right click ICON then Properties\Shortcut\Target”C:\Program
Files\Adobe\Acrobat 6.0\Acrobat\Acrobat.exe” /n.

Enjoy