Annotations & cross platform..

[fragile]

I mostly work on a linux system and may be on windows too for a while. On linux we've okular which allows annotation of books but unformtunately these are not saved in the file itself. I understand that the ability to save annotation into a book depends on the format...

So I was wondering if there existed a free ebook format that is open and allows for annotations to be stored. My files are mostly txt & pdfs and some chm, djvu etc.. I was wondering if a format as above exists, I can convert all files that I wish to annotate to that format and save it. Looking for a solution that will allow me to work with files in both linux and windows.

Any ideas/suggestions folks?