When single, double-quotes, or "/"s are used in the file name, the URL created contains spaces, which is illegal according to the HTTP specification. Saving a document in Microsoft Word will disallow you from creating a document title with these characters, but Liferay currently doesn't.
Upload a Docuement titled "Test.doc
Edit "Test.doc" within Liferay
Change title to "Test/.doc" - Liferay will accept this title
Attempt to download - you will not be able to