You can configure WordPress to search media files or attachments such as images, audio files, videos, pdf, documents etc. The files are searched based on their title, caption & description text.
To make them searchable, first of all you have to make Attachments post type searchable in the Includes section of search form as displayed below.
Then select the desired file types or MIME type that you want to make searchable in the File Types plugin option displayed in the Includes section of search form as shown below.
