Chrome and Firefox share one Cache folder

If the cache location of both Chrome and Firefox is set at R:\TEMP, both of the two browsers will store caches in R:\TEMP\Cache

Thus Chrome and Firefox share one Cache folder

As for set the cache location of Chrome and Firefox, see:
How to change the disk cache location of Chrome
How to change the disk cache location of Firefox

Some browsers can open and view PDF file directly within the browser itself

Internal PDF viewer, open PDF in a new tab in browser.
So that PDF reader software is not necessary for open PDF file from internet.
I tested Chrome 27.0 and Firefox 26.0 can open PDF file within the browser itself.
Older browsers may not support open PDF within the browser itself, e.g. Firefox 3.6