Preview app breaks PDF encoding

Hey guys,

I was surprised to see I'm no longer able to copy anything from my PDF ebook. All copied characters turned into this:

I was sure at first that maybe this file has been protected. I was wrong. Everything works fine until you save a bookmark in Preview app. When you do it and reopen the file, the encoding gets broken or something and you are no longer able to copy. It doesn't happen to all PDFs.

It's really annoying, especially that all bookmarks descriptions are lost too. Here they are:

Any idea how to fix it other? I'd like to use bookmarks feature, it's really helpful.