You share files by providing access to a particular document.
Open a Document with files that you intend to share and click on Mail. Type in an e-mail address of external user or select an address from the Address Book. Write a message and click on the Send button.

The link to your document has just been sent. The external user does NOT need to open an account or pay any fee to access the shared files.
He receives the link in his e-mail box and can view a document, open or download the attached files and added web links.
Please note that external user will not see your other files and documents or know that they exist.

The external user, however, can add notes and remarks to a document (Add Comment). This can be useful as a discussion forum or an opinion poll.