All,
I have a slow Adobe Reader and a slow Preview Reader. Same symptoms as everyone else. Takes a few seconds to scroll sometime longer. I have Yosemite 10.10.2. No virus software loaded. I have a Full gig of headroom in memory with 8 Gig capacity. I brought the activity monitor up and closed applications until there was 1 Gig of headroom in memory, all green. It made no difference to performance. I had a 84 page 40Mbyte doc with notes in it and I also opened a 2.2 Mbyte pdf that was five pages and no notes. The performance was essentially the same. I noticed in the Activity monitor that memory for Preview jumps from around 200 MB to as much as 1.1 Gig when I click on a page. It varies from 750Mbyte to 1.1 Gig and then settles back down to around 200 Mbyte when the image is rendered. That seems to be an awful lot of memory to process a simple 5 page document.
Adobe is much better than Preview but still terrible. What follows is some benchmark data that showed Preview degraded considerable with the 84 Pg pdf doc. in Adobe it is a lot faster and more consistent at 2-4 sec to render a page (this is for the 84 pg document). In Preview it sometimes just hangs for up to 30 seconds and then redisplays (this is on the 5 page document). I noticed the CPU usage went from 24% to 75% when I "clicked" on a page in Adobe.
When I opened the 84 pg doc in Preview the CPU went to 97% (AS shown on the Activity monitor for the "process" preview). That seems ridiculous but there it was. Oh it crashed while I was writing this when it was trying to open the 84 pg doc. When I reopened the 84 pg doc with Preview this time it started in the 90% range for CPU usage and jumped to 208% for a few seconds and then fell back to 91%. I clicked on a different page and observed it went to 319% CPU (as shown in the Activity Monitor for Preview) for a few seconds. I clcked again on a different page and it went to 400% CPU and simultaneously the CPU load window for the user showed at 93%.
This is "new" MacBook Pro 13" I purchased last fall but manufactured in Mid 2012 with a 2.5 Ghz CPU, Intel Icore 5, 8 Gig of 1600 Mhz DDR3 memory. It has a hybrid disk drive with 500 Gig conventional and 500 Gig Flash. There is 600 Gig of empty space. Not a Retina display. I have a 27" Mac 1020 monitor and when I display it there the behavior is the same. My belief is the testing shows this is not a screen resolution problem. In summary nothing is being stressed out on the hardware except the CPU which points directly to a software issue (CPU was idling before I opened Preview and idles back down to 7% or so after a minute or less).
This machine runs fine on all the other applications.
Any ideas out there? It seems the issue is with rendering pdfs in Yosemite and may not be an issue with the apps themselves.