Give exiftool a try, it is available from the package libimage-exiftool-perl in the repositories.
As an example, If you have a pdf file called drawing.pdf and you want to update its metadata, Use the utility, exiftool, in this way:
exiftool -Title="This is the Title" -Author="Happy Man" -Subject="PDF Metadata" drawing.pdf
For some reason the Subject entered ends up in the keywords field of the metadata in the pdf file. not a problem in some cases, even desirable, however, this may be problematic, evince and the nautilus metadata previewer do not show this but Adobe Acrobat viewer and PDF-XChange viewer does.
The program will create a backup of the original file if you do not use the; -overwrite_original switch, this means a duplicate will exist in the folder where the updated pdf is. From example above; a file named ; drawing.pdf_original will be created.
use the overwrite switch at your own risk, my suggestion is not to use it and script something to move this file to a better location just in case.
Best Answer
Megatools allow you to copy individual files as well as entire directory trees to and from the cloud. You can also perform streaming downloads for example to preview videos and audio files, without needing to download the entire file first. Megatools are robust and optimized for fast operation - as fast as Mega servers allow. This is quite fast. Memory requirements and CPU utilization are kept at minimum.
Megatools is provided in Ubuntu by the universe repository. You can install megatools in all currently supported versions of Ubuntu with the following command: