R Margin Padding
With a big font, R will cut off the end of the Y axis label text. This puts padding on the margin to give space for the big text.
pdf('h2_mf_perstudy.pdf',7,7)
par(mar=c(5, 4, 4, 2) + 0.5)
plot(dat$case,dat$SE,cex.axis=1.45,cex.lab=1.5,xlab="N Cases", ylab="Standard Error of SNP Based Heritability",main="",cex=1.5,pch=19)