Onlyoffice - pdf-viewer app - watermark - secure view

Well - i had to disable pdf-files ín only office to be able to open them in nextcloud. So - secure view is not available in “pdf-viewer-app”. i thought, maybe i could use collabore for pdf only but there i can not find the option to limit filetypes to pdf only. Secure View is a very important feature in some use cases. Is there a way to enable the secure view feature in pdf-viewer app or any other workarround to get the secure view feature availabe in nexcloud, as long as onlyoffice can nót handle all pdf-types?