Lately, I have been having trouble using Preview. For instance, yesterday I tried to open a huge pdf file (approx. 7K x 4K). It lags whenever I try to do the simplest things to the image and when I try zooming it crashes completely. My MBP is the 2014 model so the hardware should not be an issue on this one. Once, I used Skim but the interface throws me off. What else is out there?