Shared Documents is a convenient way to share your common documents to all your clients. Once uploaded and shared, your clients will be able to view and download these documents when they login to the Client Area or through the Mobile Apps.
Head over to Settings then Shared Documents. In here you can manage your documents & files, as well as optionally share these out with your clients by ticking the 'Shared' box next to each document:
Allowed files: jpg, jpeg, png, gif, pdf, doc, docx, ppt, pptx, pps, ppsx, odt, xls, xlsx, txt, rtf.
File size limit: 20MB.
If you prefer to only share files with specific/individual clients, instead of to all clients, you can do this directly from within the Client's Profile (found in the Clients area.)