I believe the W-2 form is an RTM. You can edit it in Modify Forms.

I tried changing page margins and size, but was unable to get 2 w2's to print per page no mater what pagesize or top margin I used.
 
I solved the problem by simply selecting all the fields in a window by clicking and draging.  Then I tweaked the field positions all at once to match up with the form.
 
I left the default margins and pagesize and it worked perfectly.
 
WARNING:  The Last name field needs to be moved to the right at least .2 inches before all the fields are moved as a group.  The W2 form has a wide red line between the first name and last name boxes.