Word, PDF and other files may contain the author's name, the date and time the file was created, and sometimes even part of the editing history. This "hidden" data depends on the file format and the software used.
Image formats such as TIFF or JPEG are among the most verbose. They can contain :
- date
- time
- GPS coordinates** of the image
- brand name
- device serial number
- among others
Office files may contain information about the author or the company that created the document. A simple right-click on a file can give you a lot of information.
You can delete them with the document creation software, whether Microsoft Word or Open Office
File menu > Properties
PDF files can also act as bugs. They often include the author's name. This can be accessed in the file's properties and modified using pdf editing software. To change the document author with Acrobat Writer under Windows or Mac, simply go to the menu
File> Properties.
Under Gnu/Linux, there are free alternatives such as pdf Mod which allow you to edit PDF file metadata just as easily.
The Firefox extension Exif Viewer displays JPEG image metadata. It is also available for the Chrome browser.
There are tools available for editing all metadata, regardless of the type of file to be manipulated: PDF, JPEG, GIF, etc. These tools require a little more skill to use. Their use requires a little more experience.
- Metanull](http://www.ghacks.net/download/99439/): the easiest to use, with a graphical interface available under Windows.
- mat2](https://mat.boum.org/): software with a graphical interface available under Gnu/Linux and as standard in the excellent Tails secure distribution.
- ExifTool](http://www.sno.phy.queensu.ca/~phil/exiftool/): command-line software available for Gnu/Linux, Windows and Mac OS X. There are many tutorials and examples for using it.