The "--unique" introduced in 0.3.1-r1-ebuild now forces pdfs to be opened in an existing window (if one exists). But with 0.3.1, there is a bug: opening a document or simply executing "qpdfview" does not give focus to the window. It looks as if the pdf did not get opened at all.
+*qpdfview-0.3.1_p427 (13 Jul 2012) + + 13 Jul 2012; Ben de Groot <yngwin@gentoo.org> +qpdfview-0.3.1_p427.ebuild: + Add development snapshot which includes a fix for bug #426396