A couple of years ago during a hackathon, a couple of us wrote a Qt wrapper around PDFium, the open-source PDF rendering engine which is used for viewing PDFs in Chromium. There have been a few fixes and improvements since then. Now we (finally) have made this module available under the LGPLv3 license.
QPdfDocument can render a PDF page to a QImage, and there is QPdfBookmarkModel which can be used for a bookmarks view. There is an example application: a widget-based PDF viewer.
If you want to try it out, here's how to get started:
git clone git://code.qt.io/qt-labs/qtpdf
git submodule update --init --recursive
There is some work in progress to add support for PDF in QtQuick, to treat it as an ordinary image format and to add support for multi-page image formats in general, but we don't have any particular target release date yet.