A password can be placed on a google doc by embedding it on a website page that requires a password to view. A slightly looser alternative to this is setting the documents privacy settings to "anyone with the link". This setting allows you or anyone to share the link to the document. But there is no way to get to the document through search or other means without the link. Clicking the link is required to view it. People don't realize it, but it's just as secure as a combination lock when you think about it. If you have the combination you have access. And arguably, it's just as secure as having a password protected document. The password to an online document can be passed around just as easily as a secret link. A better method than this is to give specific access to individual google accounts on a person to person basis. You can do this by clicking the blue share button on the upper right of any google doc. Sharing like this allows you to cut off access when you want. It also allows you to email anyone with access to notify them of changes. In google Apps for work, you can even monitor access to the document and have better access control options such as limiting access to accounts in your organization only.
There are a few ways t can view changes. If you have saved the files, you can open an existing folder and view them if their file name ends in .xml or .TSV. Otherwise, you can click View All or View All (In some cases, you will be allowed to view certain files, you will not be able to open other). To do this, click the file in question in a folder of your choosing in a Chrome Web browser. That is if you're on a Chromebook. In Chromium, you can browse for files that begin with .TSV or .xml. For example, right-click the .TSV/XML file in the current folder of your Chromebook and select View or Delete. This will display a link that allows you to download all .TSV/XML files. You can download the entire folder if you do not wish t download the file. In Chrome, right.