a) I think, depends on the level at which the document is shared. If it is public, anyone can find using search and edit it. If it is accessible to anyone with

a) I think, depends on the level at which the document is shared. If it is public, anyone can find using search and edit it. If it is accessible to anyone with the document link, then anyone who can discover the document can edit it. If it is shared with a list of people (or a group) then you need to login to authenticate yourself. The last is, I believe, the only solution to the problem. I don't think there exists a ubiquitous solution for sharing printable-well-formatted documents that require no special skills for formatting. .DOC will require the person on the other end to have MS Word and .ODT Libre Office (which is no way good enough for anything ATM). There are also other replacements to Google Docs, I haven't tried any as Google Docs fulfilled most of the requirements of my minimal collaborative editing but I am told that Zoho works really well.