When in WinEdt (I have version 5) you click dvi2ps and ps3pdf you obtain wrong margins,
this  is the way it worked for me:

1. Go to WinEdt
2. Options
3. Execution Modes
4. Click on dvi2ps (be careful not to confuse it)
5. Add the following in the switches area
                 -P pdf -t A4 -z
6. Voila!!!!!!

Now you only close winedt and then open it again to click dvi2ps on your file and then
ps2pdf and your margins must be right now!!

 P.S. Source that helped:
    http://people.engr.ncsu.edu/txie/publications/writingtools.html