Reading PDFs in your browser, instead of downloading them and reading them in an app like Preview, is a nice convenience. But Safari is the only major Mac browser that has a read-PDFs-in-the-browser option turned on by default. Mac OS X Hints reader Typhoon14 notes that Chrome has the same feature, but it's disabled by default; he also knows how easy it is to enable it:
Type about:plugins in the Chrome omnibox. Looking through the list of plugins, you should see a disabled one called Chrome PDF Viewer; click Enable under it.