Had that nifty bit of software for a few years barry, it comes in useful, especially when you type the scale in rather than using the drop down list.
I think we have moved away from the original problem though, --It is a plan without any scale on it. However it does have full size measurement marked on various points like between frames. To print out the plan as is would mean a plan of around 16 feet in length.
So taking the plan and the full size between frame measurement ie 12 feet, measuring that distance with a ruler in inches it came to 5 and 3/8ths of an inch. What would the conversion factor be to actually get the plan down from 16 feet in length to as it happens in my case 1/72nd scale- but that could equally be 1/100th, 1/144th etc etc.
That was the original question, and thanks to vnkiwi and derek I have near enough the answer. Then thanks to Carl who has kindly offered to resize the entire pdf file and reduce it to A0 sheets for me, although I can do that myself via photoshop and my laser printer, but the results would come out on many A4 sheets..