I am using a Brother Printer (DCP-7030) on Linux and have set it up using the drivers from the brother page. See my guide here. Unfortunately for some reason the top of the page is cut off when printing a page. After trying to set all settings in the printer configurations, nothing worked. After googling around I found a thread that helped me to fix it.

Open up your driver configuration

sudo nano /usr/local/Brother/inf/br<MODEL>rc

It should something like this

[DCP7030]
Language=LANG_USA
Resolution=600
PaperSource=Tray1
Duplex=OFF
DuplexType=Long
PaperType=Letter
Media=PlainPaper
Copies=1
Sleep=PrinterDefault
TonerSaveMode=OFF

Now find the line PaperType and change it to A4 (or whatever you need)

[DCP7030]
Language=LANG_USA
Resolution=600
PaperSource=Tray1
Duplex=OFF
DuplexType=Long
PaperType=A4
Media=PlainPaper
Copies=1
Sleep=PrinterDefault
TonerSaveMode=OFF

Now restart cups

sudo service cups restart