Chris Pirillo has made a nice tutorial that tell you how you can share Word, Excel, PDF and other files on Twitter. All you need to do is upload your file to FileSocial, and log in with your Twitter credentials. Your file is then shared with all of your contacts on Twitter.
When you upload a file, you can include a brief comment or description and a tweet will automatically appear in your Twitter account. Anyone can see, comment on and even download that file through that link.