It has been mentioned many times throughout the year of Yosemite that there are PDF performance issue in OSX 10.10. Users have been experienced lag during scrolling and zoom in/out. It is speculated that it is caused by the PDF Kit in the OS X frame work. So PDF viewing apps (including Preview.app itself) using the same framework all experienced the same performance issue in OSX 10.10. Here are three of many threads about PDF performance on OSX 10.10: https://discussions.apple.com/thread/6616093 http://forums.macrumors.com/threads/preview-pdf-annoying-slowness-since-yosemite.1806654/ http://forums.macrumors.com/threads...les-in-preview-impossible-lag-freeze.1815334/ I believe that for many OSX users, pdf viewing and annotation is an important part of their day to day work. I have not find any tech reviewers perform PDF viewing test on OSX 10.11 to confirm if the performance issue is still around in the coming OSX 10.11. Therefore, I would like to have the crowd to test out the PDF performance on OSX 10.11. Let's keep the test as consistent as possible. 1. Download the two sample pdf from here: http://dabirbook.com/uploadedfiles/files/1/book/801e32fb496d35c68fb3622f8617203e.pdf It is a 10MB, scanned PDF. http://www.jorns.ch/upload/occasionen/1/190/reference1.pdf It is a 50KB, text PDF (Possibly created by LaTEX). 2. Open them in default Apple Preview.app 3. Perform zoom in/out and scroll through the document in a very fast manner. Very fast scrolling is for mimicking the usage of navigating to some specific page in a very lengthy document. 4. Provide your system info (if possible) and the version of OSX you are using. Reply in a scale of 1 to 10. 10 for perfectly smooth. A reference for perfectly smooth can be the PDF reading experience on an iOS device. I have notice that iOS devices in recent 3 years handles PDF very well. <5 means that you experience lag constantly and it hinders your reading experience. Here is my result: macbook air 2013, core i5, ram 4gb OSX 10.9.5 (Sorry that I do not have 10.11 beta installed...) Document 1: 9 Document 2: 10 comment: (if you have comment, put it under the result for the ease of others scrolls through the results. ) --- Thank you!