data<-heatmap(data_matrix,Rowv=NA,Colv=NA,col=cm.colors(256),scale="column",margins=c(5,10))

pdf("Your-file.pdf", paper="a4", width=8, height=8)

library(pheatmap)
library(gplots)
if (nrow(table) > 100) stop("Too many rows for heatmap, who can read?!")
fontsize_row = 10 - nrow(table) / 15
pheatmap(table, col=greenred(256), main="My Heatmap", cluster_cols=F,
         fontsize_row=fontsize_row, border_color=NA)

margins = c(5, 5),
       ColSideColors,
       RowSideColors,
       cexRow = 0.2 + 1/log10(nr),
       cexCol = 0.2 + 1/log10(nc),
       labRow = NULL,
       labCol = NULL,
       srtRow = NULL,
       srtCol = NULL,
       adjRow = c(0,NA),
       adjCol = c(NA,0),
       offsetRow = 0.5,
       offsetCol = 0.5,
       colRow = NULL,
       colCol = NULL