Preview won't remember the last viewed page of PDF When I open a PDF file that was viewed days ago, Preview will open the first page.

However, when I close it and open it again right now, it will open the right (last viewed) page.

The option Start on the last viewed page was checked.
Upgrade from Yosemite to El Captain could mess up the preference files.
Delete the folder /Users/{user name}/Library/Containers/com.apple.Preview to reset settings.