Hi @miicha 
Thanks for the PR, but we have a policy against patching 3rdparty modules. Even though it looks like overkill, could you put this in a separate css file in `files_pdfviewer/css/` and load it in `files_pdfviewer/viewer.php` using `\OCP\Util::addStyle('files_pdfviewer', 'name_of_file_without_extension');`
@DeepDiver1975 Isn't that the way to go?