Hello Paul,
Thank you for your question.
I will look at creating the PDF format user guide for you.
Regards and XPS file, if you’re using a PC, this article may help, so long as you’ve got Windows 8 or later: http://www.novapdf.com/kb/convert-xps-to-pdf-216.html
In the mean time, regarding the customer payment terms; the 1 to 12 represents the number of months the customer takes to pay you. So for example, if your customers pay you in 30 days, select ‘1’, whereas if they pay you in 60 days, select ‘2’ etc.
The negative payment terms is so you can include advanced payments from customers.
I hope this helps you move on with your cash flow forecasts.
By the way, similar rules apply for the supplier payment terms too.