Like @Lix said most modern browsers have this built in it works well in chrome and firefox. This is what I do...
<object height="950" data="sample-report.pdf" type="application/pdf" width="860">
<p>It appears you don't have a PDF plugin for this browser.
No biggie... you can <a href="sample-report.pdf">click here to
download the PDF file.</a>
</p>
</object>
It degrades well if the browser doesn't support viewing PDF by letting one download it. I have looked for other solutions such as converting to html or image. But I don't like to load lots of large images and converting to html loses much of the formatting.
You can convert on your server though if your running linux with this command...
convert abc.pdf abc.jpg
-EDIT--
Firefox uses PDF.js to render PDFs. I've looked into before, but the complexity wasn't worth it for any of my projects.
Hope this helps. Aloha.
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