Preview app using 12gb of Memory - "out of storage" error - Virtual Memory

Hi guys,

Macbook Pro Late 2012

2.5ghz i5

8 GB 1600 MHz DDR3

128gb ssd

El Capitan 10.11.3

My apology if this problem has been answered somewhere else, I tried looking for it a lot but couldn't really find any solution.

Problem:

I have these few pdf files (each ~200mb) that I use a lot on a daily basis.

They are locked/secured - thus every time I highlight/edit a file - preview creates a duplicate that allows me to edit the file.

Right now I have 4 untitled documents that preview had created for me so I can edit them.

My hdd space is 0 kb...

Stats from activity monitor-

Preview using 12gb of memory and 10.7gb of compressed memory

Memory being used = 6gb (app memory = 4gb; wired memory = 2gb)

Cache files = 1.7gb

Swap files = 8.5gb

After closing down Preview and all the documents and not saving them (which i never do)

My hdd space available = 9gb

physical memory used = 4.5gb

Cache files = 1.5gb

Swap files = 1.25gb ****

I kept wondering why my harddrive space would be taken up so much when I just go on my laptop to work and read these documents.

Any one have any solutions for me? Advice? How to avoid this perhaps?

Thanks for everything in advance,

Ari