Band-Aid Solution: Replace the Yosemite PDFKit with the Mavericks Version As suggested at https://discussions.apple.com/message/27639834?ac_cid=tw123456#27639834 a band-aid solution is to replace the Yosemite PDFkit with the one from Mavericks. I have done this myself, and so far performance seems better with no ill effects. From the thread:
If your Time Machine backup spans from before your installation of Yosemite, you can pull it from there.
Probably I have done something wrong, but after completing the procedure with the file provided here, my mac stopped functioning (finder crash) and i had to restore my OS.
Sorry you had the trouble. I just verified that the file linked above matches what I extracted from Mavericks (if you open Terminal and enter 'shasum PDFKit.framework.zip' you should get d09abd9a280fded8dd6441c4b737b437d209e375). Did you unzip it? You do need to do that. Similar to applications on a Mac, the PDFKit.framework file is actually a folder that appears in Finder to be a single file. Thus, to actually make it a single file, I zipped it.
I followed in instructions above and everything seems to be functioning normally. PDF performance seems better, but still slower than I expect it to be.
This work-around works I came across this thread due to the crazy-slow browsing of PDF plans sent to me by the Architect I work with. Just to let you know that what user "Adhir" mentions in his post of January 24th in this thread works.... "A workaround for those of you who haven't found it - at least for viewing - is just to use quicklook. PDFs are as fast as they were in Mavericks this way. Just find the file you want to see in Finder and hit the spacebar." Zooming scrolling and panning of the PDF plan files is way better and completely useable when done through "Quicklook" I hope you have a similar experience. This may also help Apple figure out what the bug is...
I can confirm that my particular problematic PDF scrolls and zooms smoothly in Quicklook. However - sadly - quicklook has a maximum zoom level that isn't enough for what I need. But yes, it does show that PDFs can be viewed in pre-Yosemite glory. Bottom line, this is a bug that Apple knows about and needs to address.
Just FYI - this is fixed in the developers preview of El Capitan. The new OS is actually amazingly responsive; really impressed.
"WARNING: the following method below is NOT a fix!" Having said that, I have found a "workaround" that may suffice for those who had experienced the problem. I have found that while viewing pdf files on preview with: resolution scaled at highest (1680 x 1050) pdf file opened in Preview with Continuous scroll Preview opened with size more than half the screen (making the window smaller will somehow help) will experience slight "lags" while scrolling. This only affects with Preview, scrolling in Safari is smooth for me. For those who encountered the same situation and is frustrated with Yosemite, I have noticed a workaround that can at least let me scroll smoothly: Link an external monitor to your macbook and view the pdf files there. I might want to add that both the external monitors I tried weren't "retina" displays. I tried it with a 24" display via VGA/Lightning adapter and the other 55" HDTV via HDMI cord. The 24" displays run at 1680x1050 while the 55" runs at 1920x1080. Both are scrolling perfectly smooth for me. Like I previously said, this is NOT A FIX, merely a temporary solution until Apple fixes this. For those whom are frustrated with Apple/Preview, you can give my solution a try. Hope this helps.