Could not find how to do it with qpdf or pdftk or even a gui tool.
Edit:
Solution pdftk A=oldpdf.pdf cat A output newpdf.pdf
This removes all metadata and also the attachments.
From Wikipedia, the free encyclopedia
Linux is a family of open source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991 by Linus Torvalds. Linux is typically packaged in a Linux distribution (or distro for short).
Distributions include the Linux kernel and supporting system software and libraries, many of which are provided by the GNU Project. Many Linux distributions use the word "Linux" in their name, but the Free Software Foundation uses the name GNU/Linux to emphasize the importance of GNU software, causing some controversy.
Community icon by Alpár-Etele Méder, licensed under CC BY 3.0
You might try printing the PDF as a PDF.
That worked but it removed bookmarks. I added solution to the post.