Can I hide the Adobe floating toolbar when showing a PDF in browser?

I think that is the preference of the user.

What you can do is to add #toolbar=0 to the end of the URL.

For example,

http://DOMAIN/FILE_NAME.pdf#toolbar=0

Something you might want to do is:

<embed src="MyFile.pdf#toolbar=0&scrollbar=0&navpanes=1" width="530" height="300" />

For details of parameters, please visit PDF Open Parameters.

What you're looking for isn't possible. Read the answer by Leonard Rosenthol (Adobe's PDF architect) on the iText mailing list: http://thread.gmane.org/gmane.comp.java.lib.itext.general/55112/focus=55120

Since version X of Adobe Reader, there is a new mode called "Read Mode", which is the default viewing mode when you open a PDF in a web browser. In "Read Mode" you can find a semi-transparent floating toolbar containing basic reading controls, such as page navigation, print and zoom.

Unchecking "Display in Read Mode by Default" can be done from Edit > Preferences > Internet in Adobe Reader X but it there is no way to disable "read mode" programmatically.