Vipin PG 
WhatsApp introduced Document File transfer in their Android application so that doc and pdf type files can be sent through the application. The new feature is not available in the Google Play Store version. Currently, it can be downloaded from the WhatsApp website. After the testing is completed, it will be available in Google Play Store also.
WhatsApp is continuously updating the application with new features every time. Recently they introduced backup to Google Drive, earlier, the Voice Call, etc. Now they raised the Document Transfer feature. PDF and DOC files can now be transferred using this feature. With the addition of this feature, directly any types of files such as jpeg, png, gif, pdf, doc, mp4, 3gp, etc., can be sent through WhatsApp.
The feature is available in the versions above 2.12.489. If your application is not updated, you can manually update it by downloading it from the WhatsApp website.
https://www.whatsapp.com/android/
It is actually one of the great features of WhatsApp and waiting when its going to be live for everyone. Today I read about one more feature of WhatsApp in which you can use it as a document store where you can store PDFs, GIFs, images, videos, voice memos and so on, just by creating a group which includes only your number.