The PSM_ADDPAGE message adds a new page to the end of an existing property sheet. You can send this message explicitly or by using the PropSheet_AddPage macro.
PSM_ADDPAGE wParam = 0; lParam = (LPARAM) (HPROPSHEETPAGE) hpage);
No return value.
The property sheet is not resized to fit the new page. The new page should be no larger than the largest page currently in the property sheet.