What types of files can I send using the Chat API in WhatsApp?
Text, Pictures (PNG and JPG), Audio (OGG) and Documents (PDF). You can send links containing any type of file (documents, video, audio, etc.), as well as geolocation, contacts and V-card business cards. Maximum file size 60 megabytes.
You can learn more about the process of sending files here.
Please note that files of the "document" type have no description and therefore cannot use the "caption" parameter.