Google have released a mobile version of Google Documents for devices running Android and i(Phone)OS. This will help you to view PDFs, .ppt, .doc and .docx files that you have uploaded to your documents list, without needing to download the file.
The new viewer also allows users to seemlessly switch between pages and pan/zoom within a given page. Right now, pinch-to-zoom is only supported on the iOS devices. I wonder how long this exclusivity will remain? To check out the official and complete blog post about this new update, visit the Google Mobile Blog here.