I had just this same question this morning, hence my new membership. Turns out that page layout and dimensions are all stored in the XML files in the EA/ModelPatterns folder, under where you've installed EA. I had to experiment with the values I ultimately used, but it seems to work, so far. "grep" [or "awk"] for "PaperSize", and you'll see values of 1 (Letter) or 9 (A4). I've changed them all to PaperSize=1. That's not enough, because there are document dimensions, as well.
Those attributes are DocSize.cx=815 and DocSize.cy=1063, for US Letter. So my heavy-handed soution went something like this (Under cygwin ... I install apps on D:):
$ cd /cygdrive/d/Sparx\ Systems/EA/ModelPatterns
$ mkdir Archives
$ cp *.xml Archives
$ for this in *.xml; do
sed -e 's;PaperSize=.;PaperSize=1' -e 's;DocSize.cx=...;DocSize.cx=815;' -e 's;DocSize.cy=1...;DocSize.cy=1063;' ${this} > /tmp/${this}
done
$ mv /tmp/*.xml .
Now, all my new projects are layed-out correctly, for me.
Oh, yes, the guys at work complained about this solution, and I somewhat agree with them. Though the analogy was bad - one guy said it was like changing gears by replacing the gearbox. I say that I'm just not using the clutch.
You be the judge.
Cheers,
Payter.