If you print a map, either to paper or to PDF, then the Page Size that you set in PTMapper will affect the paper print or PDF that you produce.
For example: if your map in PTMapper has a Page Size that is set to A3 then you must select a printer tray on your printer that has A3 size paper. But, many printers which have both A4 and A3 will often default to A4, unless you select something different. So if you print an A3 map without selecting an A3 printer tray then you may end up with 4 A4 sheets instead..!
This also applies when you are using PDF software as many PDF software packages will also default to A4 size.
For example: if your Page Size in PTMapper is set to A3, unless you change the setting in your PDF software to match the Page Size in PTMapper you are very likely to produce 4 A4 PDFs instead of a single one at A3 size.
So before creating a PDF, check that the page size in your PDF software settings matches your map Page Size in PTMapper.
Most PDF software settings are similar to those shown in the following screenshots:
First, select your PDF software (PDFCreator in the example below) and then select Preferences:
Next select Advanced:
In the Advanced screen there should be an option to select different page sizes, so pick the one that matches your map Page Size in PTMapper:
Click OK until you are back at the first screen, then click Print and create your PDF.