With the help of WaSend: WhatsApp Any File Send you can send PDF documents, zip files, songs, and even APKs for Android apps. You can send practically any file type you want.
The procedure is very simple: WaSend: WhatsApp Any File Send 'tricks' WhatsApp into believing that instead of these files you're actually sending videos. This means that the user you send the documents to will just have to open them from WaSend to 'open' the videos and access the real files.
It's important to keep in mind that you can't send files larger than 150 MB and that when you send them the program will create 'video files' of no larger than 15 megabytes.
WaSend: WhatsApp Any File Send is a very interesting add-on for WhatsApp that turns out to be especially useful for sending all sorts of work documents quickly and effectively.
Requires Android 2.2 or higher