LibreOffice does not come to front when opening a document, if there is a document already open. Opening LibreOffice by double-clicking a document opens the document normally. If a document is already open, double-clicking a document opens the document, but the application remains minimized in the taskbar. I have only seen this behavior since updating to LibreOffice 4.2.
already reported before. *** This bug has been marked as a duplicate of bug 47049 ***