Do you get the message:
The printer's paper size has changed since the last time this document was paginated. Repaginate to the new paper size?"
Most likely, you are in a country or using a printer where the paper size is set to something other than US Letter.
The cause is simple: when Screenwriter opens a new document, or creates a document from the Default template (or any template), it compares the paper size of the printer that was selected when the template was created.
To eliminate that message every time a new document is created, the solution is equally simple:
1) Using FILE > New (using Default template), create a new, empty document. You WILL get the warning message about the paper size changing.
2) Using FILE > Page Setup (Macintosh) or FILE > Printer Setup (Windows), select a printer and your desired paper size.
3) Using FORMAT > Make Default for All New Documents menu command. You might get an informational alert:
This makes sure the Default Template has YOUR desired paper size, rather than the standard US Letter paper size.