Update:
I found the service menu on my PVM-20N2E!
1. Hold the MENU/EXIT button and press ENTER
2. You will see a text like "Ver 1.30"
3. Press ENTER two times
4. You will see "00 PKUN 0000"
5. You are now in the adjustment section of the service mode!
6. Use the buttons for LINE A and LINE B to scroll through the options
7. Use the arrow buttons to change the value
8. You can press the RGB button to save your adjustments
On my PVM all the settings are numbered from 00 to 64.
Here are some usefull settings to adjust screen size and position:
12 V CENT - vertical alignment
41 RGB CLAMP - horizontal alignment (maybe this is not the right method, but it works)
50 H SIZE - horizontal size
56 V SIZE - vertical size
I still need to play around with the RGB settings and the brightness and such.
More on that later!
I'm pretty sure this method works on all following PVM's:
PVM-14N2A/E/U & PVM-20N2A/E/U
PVM-14N5A/E/U & PVM-20N5A/E/U
PVM-14N6A/E/U & PVM-20N6A/E/U