How to get plots in several pdf pages using ggplot2

The ggplus wrapper appears to do what you want. I changed a couple of things in the code block below from your original: facet_wrap is commented out, and file is moved to ggplot so that it doesn't have to be re-specified in each geom_*:

gg1 <- ggplot(file) +
  geom_line(aes(x=TIME, y=var1, colour = "z1")) +
  geom_line(aes(x=TIME, y=var2, colour = "z2")) + 
  geom_point(aes(x=TIME, y=var3)) +
  # facet_wrap( ~ ID, ncol=5) +
  xlab("x") +
  ylab("Y") +
  ggtitle(" x ") + 
  scale_colour_manual(name="Legend",
    values=c(z1="red", z2 ="blue"),
    labels=c("X","Y")) +
  theme(legend.position="bottom")   

devtools::install_github("guiastrennec/ggplus")
library(ggplus)
pdf("need10.pdf")
gg10 <- facet_multiple(plot=gg1, facets="ID", ncol = 4, nrow = 4)
dev.off()