PDF24 provides a free online PDF Viewer which runs directly in your browser. You don't need to install any further software to view PDF files online. The PDF24 Viewer has a lot of nice features e.g. view in full screen mode or print a PDF file. The PDF Viewer is Java based and can be embedded into your website.
Open the Online PDF Viewer
You can embed the Online PDF Viewer into your website to show PDF files. How you can do this is explained on the following page:
Embed the Online PDF Viewer