I have this problem also, I'm using an older version of Word though (2003) that doesn't give you the option of pasting with original source formatting or keep text only. I'm trying to figure out how to select text and reverse its direction, the Word documentation seems to indicate that it is possible to do this but I haven't figured it out yet.
Update: I've figured out how to do "keep text only". After you paste, there is a little icon at the bottom of the pasted text in Word 2003. You click on the icon, and there is a "keep text only" option. This seems to work. It also alters the Hebrew font used.
Edited by firstname.lastname@example.org, 21 October 2013 - 10:15 PM.