Currently Being ModeratedOct 22, 2012 5:32 PM (in response to dd26)
So I figured out what happened by looking at my /Users/myusername/Library/Preferences/com.apple.Preview.bookmarks.plist file. Basically, I had renamed a folder in the path to the pdf file that I was viewing. So the /Users/myusername/Library/Preferences/com.apple.Preview.bookmarks.plist file had the old path to the file in it. So I just had to close Preview, edit the path to the pdf file in the plist file, and now my bookmarks are back! If you do this, make sure you close Preview first - otherwise it will write over your edited plist file with the original plist file when you close it). If you are uncomfortable editing a binary plist file (like I was), use this command in Terminal to convert it to xml: "plutil -convert xml1 /Users/myusername/Library/Preferences/com.apple.Preview.bookmarks.plist". Then use a text editor to open the file and replace all instances of the old path to the pdf file with the new path. Reopen the pdf file in Preview, and your bookmarks should magically appear un-grayed out again!
Currently Being ModeratedJun 21, 2013 12:36 PM (in response to dd26)
Had the Same issue except it was resolved much easier for me by just going to the file\ rename within Preview and when you change the filename there it won't gray out the bookmark tabs. If you change the file simply by clicking on the file name it will gray them out as you said.
iMac, Mac OS X 10.8.4