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.

FxPDF is a rewritten in Action Script 3.0(AS3) original libHaru PDF library project developed in C language.
It is generating PDF files on client side by using native Action Script code in Adobe Flex and Adobe AIR projects.
If you want to have a test, please follow the FxPDF Examples
For details, please visit here.

Apvlv is a cross platform open source software.

Like Vim, Apvlv makes people reading their PDF files just like using Vim.

So, Apvlv bindings lots of Vim command and its behaviour is like Vim. For example, < Ctrl-f > to forward page, < Ctrl-b > to previous page, ‘k’,'j’,'h’,'l’ to scrolling a page up, down, left or right, and so on.

And, Apvlv can understand that how many times you want to run the command.

The only thing you need to do is typing the number before the command. For example, typing ‘50′ and < Ctrl-f > will go forward 50 pages, typing ‘30′ and < Ctrl-b > will go previous 30 pages.

What’s more import is apvlv can support view a directory as content of a pdf document. Pressing ‘k’ or ‘j’ to move selected up or down, ‘h’ or ‘l’ to collapse or expand a dir, and press ‘t’ will open the selected document in a new tab.

for the last source code and pre-compiled binary, please visit http://code.google.com/p/apvlv/