how to filter ojs file only pdf file when upload subnission file?
OJS does not restrict the file types one can upload. Maybe you can modify the upload File method in lib/pkp/classes/file/FileManager.inc.php to achieve this.
how to modifity the upload file in FileManager.inc.php?
sorry I’m new to OJS and PHP so I can’t provide you with exemplary code.
You will need PHP skills to accomplish this. If you are familiar with PHP, consider checking out this parallel thread, where a similar modification is discussed: