How to hide (remove) 'Owner' and 'Computer' information on PDF file?

Those details exist for files other than PDFs. The Owner and Computer details you wish to remove are used for permissioning and only exist on your local computer. When you share that file elsewhere, the details will not be in the file.

If you want to remove attributes and metadata from a PDF without using additional programs, you can open the PDF with Google Chrome, click print, and then select the Save As PDF setting from Chrome. Save the PDF and you'll see the data cleared when you go to File -> Properties in a PDF that was previously protected.

Sometimes, Adobe PDFs are strange in that none of your "properties" tab based advice worked, as least as far as removing names from a Comment box. They seem to do incremental or one-place only author name removals. If you like to comment in documents, then make the first comment, so that the comment box will pop-up. Then, remove the author's or login name and select "Make Current Properties Default" so that the remaining comment boxes also don't show the author's names.

Unfortunately, you'll need to follow the other advice on this page to remove the overall author's name, like going to Property tabs.

Very annoying.