I am using Illustrator CC and I need to create a large image document
85cm X 200cm, but the printing guy is asking me this document to be in
700dpi. How can I set, emulate or create this within Illustrator? Illustrator only allows me to create
150dpi, or 300dpi.
85cm x 200cm is 33.4646in x 78.7402in. To set it at 700ppi (pixels per inch) you need to multiply that by 700, so your document should be: 23425px x 55118px, independent of whatever ppi you choose in Illustrator.
That is a LOT of pixels, particularly because illustrator outputs a vector file that is 100% scalable (unless you are using raster images within). 700ppi is overkill for a sign of that dimensions imho, you could easily get away with 150ppi, or even 70ppi.
Regardless, you may be better creating your file at 1/10 scale – 70ppi is a much more manageable 2343px x 5512px.