SumatraPDF is popular. It's also open-source and some scam artists take advantage of that.
They take SumatraPDF, rename it and bundle additional crap software that takes over your browser and does other questionable things.
Unless you want your computer to be infested with malware, unwanted browser toolbars etc., use the original SumatraPDF, downloaded from our official website.
List of SumatraPDF ripoffs that we know about: