How can I open pdf file in my browser with the Foxit pdf reader plugin?
It worked before, but now when I click on a pdf link it automatically downloads it.
I think you are missing this setting. Go to EDIT -> Preferences into Foxit Reader application.
Even if this is not exactly an answer to your question, the latest versions of firefox include a built-in PDF reader that lets you read PDF files without the need of an external plugin.
So you shouldn't need to use Foxit Reader if you don't want to.
If you prefer to use Foxit readeer anyway, then disregard this.