Old / Vintage

Hi Very very vintage setup - if this offends, please look away now. My Mac recently died, I am using a borrowed 2009 Quad core Mac Pro while I sort out what to do next. It badly needs updating as it is still on OSX 10.6 It has Adobe CS5 and Vectorworks 2010. I will probably replace CS5 with CS6. Any idea what OS I could take it up to without breaking Vectorworks or CS5/6? I know it won't be very recent, but anything would be an improvement on 10.6 in terms of security.