I've used the LEFTMARGIN, RIGHTMARGIN, TOPMARGIN and BOTTOMMARGIN style attributes to set the margins for my document, but they're not having any effect.
This is a known bug in SAS version 8. These style attributes aren't honoured. The workaround is to use the corresponding SAS system options in an OPTIONS statement.
The problem is fixed in SAS 9.1.3 (and possibly earlier).