When designing web sites should document files such as PDF, DOC, XLS, should the documents open in a new window/tab or in the current tab?
Jakob Nielsen has an (old) article that deals with your issue: Open New Windows for PDF and other Non-Web Documents
How about having 2 actions for documents: Download and View? Here's some examples:
I would suggest that you open your documents in a new window. Mainly because some documents like pdfs could possibly break browsers navigation if a user clicks a link inside. By opening documents in a new windows you can prevent this. In my experience its more frustrating to completely lose my prior navigation that having a document open in a new window/tab.
Also note, for accessibility reasons you should let the user know when a page/document is going to open in a new window.
You have no control* over document formats that the browser doesn't natively support. They may open in the browser with a plugin. Or they may download. Or they may open in an external application of the browser and/or end-user's preferences.
As such, you should not open a new window, as you have no control over it.
Instead, let the end-user know what kind of file they are about to click on, and then they can handle the rest to their own personal preferences.
- the one exception is that you can force the save dialog to appear if you stream the file from the server. That's sometimes a useful thing to do.
I've always liked providing the document type and size in the link and letting the user's native applications open the file.
e.g., [a href="report.pdf"]Annual Report (PDF, 233Kb)[/a]
This lets the user know that it is not a web page (and doesn't act like one), and also gives them information on the size so that if they think it's too big or will take too long to download, they can skip it.