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What commands must I issue irreversibly to remove all metadata
from foo.pdf? Assume embedded images are already clean.
I got the impression from
https://gist.github.com/hubgit/6078384
that
exiftool -all:all= foo.pdf
qpdf --linearize foo.pdf bar.pdf
might suffice, but it wasn't clear to me whether it was an
entirely complete method. There was some talk of pdftk and an
"info dictionary" that I didn't understand.
There is a tool called MAT (Metadata Anonymisation Toolkit) that can remove metadata from a number of different formats. In Ubuntu, this is how I use it:
sudo apt install mat2
mat2 filename.pdf # you will now end up with a file called filename.cleaned.pdf
mat2 --inplace filename.pdf # this will overwrite original file with the new one, effectively removing the original file
Note that the cleaned file will have a smaller or larger filesize compared to the original.
There is a lightweight mode (just add --lightweight) you can try if the cleaned image with the commands above produced significantly large files, as in pdf files. But this might leave some metadata. Use the exiftool command to find out if the cleaned image is still leaking any metadata.
mat2 will (at least some times) change your PDF version (e. g. from 1.4 to 1.5)
mat2 increased the file from 1.1M to 4.4M. I do not suggest it.
May 29, 2021 at 17:48
mat2 -L or --lightweight) that prevents rendering the text as images, but might leave some metadata intact.
cpdf -remove-metadata input.pdf -o output.pdf
I haven't verified it myself, yet but cpdf is a very reliable to useful tool, available here, free for non-commercial use, and available as a precompiled binary for linux command line.
And the file size is smaller at the end ;)
pdftkorqpdf: askubuntu.com/a/1300265/632237