If you annotate documents using Okular, you might be saving the file as a document archive. This is typically a file with extension
The document archive file is actually a zip file with 3 files inside it. First is your original document (PDF, DjVu or other format) with its original filename. The other two files:
metadata.xml hold information about your file and its annotations.
Okular does not provide any user interface to extract out the original document. But since we know it is a zip file, we can open the
.okular file using any unzipping tool and extract out the original document! 😊
Tried with: Okular 4.13.3 and Ubuntu 14.04