I've recently came across an R package called 'officer' that makes it really easy to export editable figures/graphs (base or ggplot) to an Office application. This makes it really easy to modify figures for presentations or in my case a poster. Every element will be generated as a text/shape etc so you can change colors, text sizes, move them around etc. Also looks as though you could generate an entire presentation or document if you wanted. Figured I would share the knowledge. Here is a link to the vignette for exporting to powerpoint. I was able to follow it exactly and achieve the desired result but if you have issue feel free to reply. There are also other vignettes for the package on CRAN if you are interested in other applications.