Hi guys,
I'm not sure if this is the right place to post this topic but...

Please help me out figuring out the cause of my PC running very slow sometimes and taking up huge amounts or RAM, immediately associated with intensive hdd activity ( I can actually hear it ).

First, my workstation is comprised of:
Athlon X2 240 running at 3.0 Ghz
4GB DDR3 1333
openSUSE 12.2 X64, EXT4 fs

I experience high RAM usage when opening PDFs for example, a 30MB PDF is making Ocular using up to 1.5GB of RAM and I can't scroll the PDFs pages wthout locking up the PC and having to either kill the process or wait several minutes to catch its breath. I open up Firefox on 9gag and that also takes up over 1GB of ram and scrolling is not smooth. Meanwhile I notice high hdd activity ( swap ? ). Now I know 4GB of RAM is not rocket performance but I cannot read PDFs by scrolling them, I have to wait for each page to load up, and if I force a scroll it causes the whole session to lock up and struggle, even the mouse pointer goes haywire.
I did a check on my HDD and it shows healty. Could this be a swap configuration error or is there a "checklist" of things for me to check in finding the issue ?

Thank You !