fix incorrect usage example for --default-header

src/pdf/pdfarguments.cc

@@ -228,7 +228,7 @@ PdfCommandLineParser::PdfCommandLineParser(PdfGlobal & s, QList<PdfObject> & ps)
 
 	section("Page Options");
 	mode(page);
- 	addarg("default-header",0,"Add a default header, with the name of the page to the left, and the page number to the right, this is short for: --header-left='[webpage]' --header-right='[page]/[toPage]' --top 2cm --header-line", new Caller<DefaultHeaderFunc>());
+ 	addarg("default-header",0,"Add a default header, with the name of the page to the left, and the page number to the right, this is short for: --header-left '[webpage]' --header-right '[page]/[toPage]' --margin-top 2cm --header-line", new Caller<DefaultHeaderFunc>());
 
 	addarg("viewport-size", 0, "Set viewport size if you have custom scrollbars or css attribute overflow to emulate window size",new QStrSetter(s.viewportSize,""));
 	addWebArgs(od.web);