From version 2.2 you are able to open documents in mobile apps, to preview them or to use options; to share them (via other apps), download them to your device or store them to cloud storage apps (if using) – Google Drive, Dropbox etc.
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To begin, you will need to open a deal and go to Document tab (3rd option on bottom navigation). Touch on the file you would like to open and it will render the preview in the next screen.

While in preview screen you have option in top right corner to share the file (for the PDF type of files, option will be located on bottom) using other apps you have in your phone (email apps, messenger apps) or to store the document as a File on your phone or cloud storage service (Google Drive, Dropbox etc.):

After share button is clicked, you will have options to perform on the document. You can share, copy, print, save as File or as draft to your phone or store document on cloud.