I have a 2008 iMac running OSX Snow Leopard 10.6.8. I use this machine for work and it does just that - it just works! In the main I use Adobe CS5 (which is paramount to my duties and well up to my requirements, hence not having upgraded to later versions) and am getting to the stage where the software I look to buy these days requires Mavericks or above. The last thing I want to be doing is upgrade to find that elements of my daily productivity are hampered by software starting to not work and other associated problems causing me to dig deep for upgrades I really don't need. My question is whether I can keep 10.6 on my machine while also being able to download Mavericks or Yosemite and be able to switch between the two as (if) necessary until I know everything is OK?