The converted PDF's page size is not the same as the size specified in "General Settings > Page Size".
The application might decide which is the best page layout for you, e.g. Microsoft Word. As a result, Right PDF/ Gaaiho PDF Converter concurs with the application's setting. In other words, even if A4 is specified in printer properties, Right PDF/ Gaaiho PDF converter would create PDF according to Microsoft Word's "Letter" size.
If you are using Office 2003, under Tools > Options, choose "Print" and uncheck "Allow A4/Letter Resizing".
If you are using Office 2007/2010, open "Word Options" from the left-upper corner menu, in "Advanced", choose "Print", uncheck "Scale content for A4 or 8.5 x 11" paper sizes".