Office documents and pictures contain lots of information in the meta tags that may deanonymize their author. Before uploading them to the Internet you should remove this meta data.
Pictures and Fotos
Meta tags in pictures and image files may be deleted in the file manager with a right-click. Choose the option “Remove meta tags” in the context menu. You may select and clean several files at once if you press the <CTRL>-key simultaneously. In the properties dialog of the file manager you may check the success of your attempt to delete the meta information.
Office Documents, PDFs, MP3….
You can use the Metadata Anonymisation Toolkit (MAT) to clean OpenOffice documents, Microsoft Office documents, PDFs and MP3 and FLAC sound files. Archives are supported too. Simply click with right mouse button on the file in the file manager and choose the entry “Metadata Anonymisation (MAT)”.
Alternatively you may open the GUI of MAT. A menu entry you may find in the applications menu in the group “Utilities”. Add the files you want to clean to list clean the list. The cleaned files are stores in the same directory like the original files with the extension “.cleaned” in the name.
Documents from unknown source
MAT for documents and “exiv2” for fotos are useful tools to remove meta data from your own, self created files. Both can not anonymise the content, nor handle watermarking, steganography, or any overly customized metadata field/system from unknown source. You have to clean such documents more aggressively:
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You may print the document with low resolution and scan it afterwards. For scanning of text documents you may use black/white color scheme and a low resolution too. Clean the scan images as descripted above.
from here