I know that documents and images embedded in them should be converted to CMYK before printing. Recently out of curiosity I printed both the RGB and the CMYK version of a photo (the CMYK version painstakingly tweaked to look as close to the original as possible) on a regular office printer. To my surprise the RGB file's print turned out to be noticeably brighter and closer to what appeared on the screen compared to the CMYK file's print.
I regularly volunteer as a graphic designer for small charity organisations who print their posters on their common office printers. Would it be worth to leave the PDF files I send them as RGB, and trust the printing machines to convert the colours to the best of their ability, or should I stick with what I learnt, and keep converting everything to CMYK?