PDF settings for large format printing

We are using Corel X6 sending PDF files to Ergosoft PosterPrint RIP software, and are having colour problems. We are new to signage and have a background in printing - so using CMYK is natural for us, but need to know also what is the best colour palette to use for signage.

Can someone also tell me the best settings for document and PDF please.

BTW we are also creating cutcontour and perfcutcontour lines for a Summa Cutter on the artwork (and note there is no Summa Cutter profiles in Corel). Neopost have suggested we use 100% magenta for cutcontour and 100% cyan for perfcutcontour. This means we can't export files converting colours to CYMK as we lose the cut lines.