I recently encountered a running out of application memory issue, and after much googling didn't seem to find the true root of the problem. However, I have found a suitable answer for now...

The other day I was doing what I always do, using Illustrator and InDesign, along with a few other applications all open at the same time, and all of a sudden out of the blue my laptop fans start buzzing hysterically and I'm flagged a message that says I have run out of application memory. Immediately the programs I am running freeze up, with the only solution to shut down and restart. This happened at least 5 times in quick succession before I was ready to tear my laptop in half or throw it through the window. This really shouldn't be happening, I have 16GB RAM, which is far more than I needed for the job in hand and to add insult to injury to frustration, my free apple support had ended just 7 days before this episode....

This all seemed very bizarre, the only thing I had done differently was move my work space to downstairs. My laptop obviously didn't like the Feng Shui down here...

But! I have found a handy work around, plus I think I may've stumbled across the answer myself. After googling and contacting Apple Support through Twitter I was advised to update my system to Yosemite. This I wasn't willing to do, I didn't want to lose anything on the off chance that this might work. What I did find online was a handy tip about checking out my activity monitor to see what was guzzling all my juice. Within the activity monitor I noticed that there were two items on the list using an awful lot of energy, these being the Kernel and the Finder Web Content. The Kernel is the operating system and so without that running you have in essence switched off the computer, it needs to be running - but what about this Finder Web Content? I found that I could force quit that through the activity monitor and that immediately solved the problem on a short term basis. That seemed to solve the problem, however, a few days ago the same thing happened, however, I was able to act quickly with this handy tip and so didn't lose any of my work. As the fans started, I immediately checked out my activity monitor, however, this time I felt I had sussed it out...

In both cases I had been sent a word document that had been saved as a pdf by my client, through running it through mac pages.

This was the root cause of the problem. I asked the client to send the original pdf and worked from that instead. The problem was solved. So, to sum up. If your system looks like crashing, act quickly! Check out your activity monitor to see how the energy is being distributed across your system and quit anything unnecessary - you may just save your work in time. If you receive documents that aren't in their original format, always try to find the original document as you will  be able to work more effectively and meet your clients needs more quickly.