Collabora Online is a collaborative online office suite based on LibreOffice technology. This is also the source for the Collabora Office apps for iOS and Android.
It is possible to export so called "hybrid PDF" from Collabora Office, LibreOffice etc. It contains the original ODF content. When such hybrid PDF is opened from Collabora Online, it opens as a read-only ODF file. The problem is that in this case the commenting is disabled. I would expect the same functionality as for normal PDFs, or the same functionality as in desktop Collabora Office or LibreOffice, i.e. full editing for the ODF, and export again as hybrid PDF.
It is possible to export so called "hybrid PDF" from Collabora Office, LibreOffice etc. It contains the original ODF content. When such hybrid PDF is opened from Collabora Online, it opens as a read-only ODF file. The problem is that in this case the commenting is disabled. I would expect the same functionality as for normal PDFs, or the same functionality as in desktop Collabora Office or LibreOffice, i.e. full editing for the ODF, and export again as hybrid PDF.