The problem is, to read a PDF, you need a Reader - a client application that will render the document, since it's essentially just a set of vector instructions (give it a try, open a PDF in a text editor).
You would either use Adobe Acrobat Reader (a bloated piece of software, that gets bigger and bigger over versions and consumes endless amounts of resources) or free readers, like the lightweight Foxit Reader. But still, the fact remains you have to download the PDF document and open it in a Reader, or use a BHO (Browser Helper Object - an ActiveX for IE or an add-on for Firefox) - which is essentially the same.
Macromedia FlashPaper allows you to save any document you want as a Flash file. It is viewable in a Flash player, which you probably already have in any browser you use, on any OS available. Here's a sample I've just created of the Gettysburg Address:
You can zoom in and out (+ and - buttons), browse through the document, search in it, copy from it and print it.
Using the application is very simple: drag any document (text, Word, or a PDF) into the single window, and select "save as FlashPaper". Alternatively, the program adds a device driver to Windows, so you can print directly to FlashPaper from any application.
You can download a trial version (30 free days) of FlashPaper from Adobe and play with it.