I've been using PDF-XChange for many years. I've replaced Viewer with Editor, which is improved version of old Viewer. It creates optimally sized PDFs and the PDF Editor is lightweight and very easy to use. I find that the Editor's features are much more detailed than competitors' ones. Plus, is you want only Free version, again, Editor is number 1 here

The best pdf viewer I've ever used. The free version is excellent and far easier to use (and faster) than Adobe Reader. The new version has some new nice futures such as change colour, fonts or main background according to own style and mood, close even a single opened tab without closing the Viewer itself and some others. I'm happy to use it.