Google Docs Viewer is an undocumented feature of Google docs, with it, you can quickly view documents online without leaving your browser, of course, the documents should be online. PDF documents, PowerPoint presentations, and TIFF files are supported.
you can directly put the url of online document to the end of “http://docs.google.com/gview?url=”, for example, http://docs.google.com/gview?url=http://soft.rubypdf.com/itext/sample-ch01_Lowagie.pdf
and you can easily embed the online document into your webpage
<iframe src=”http://docs.google.com/gview?url=http://soft.rubypdf.com/itext/sample-ch01_Lowagie.pdf&embedded=true” style=”width:600px; height:500px;” frameborder=”0″>
btw, Google Docs add OCR support to PDF and Images, but if you want to search scanned PDF or Tiff, you still have to upload them to your owner Google account.