How can I add some hebrew words to an english document

[Pinchas]

hebrew keyboard, right to left typing, rtc

[ve3oat]

Not sure that you can do that (adding R-L typing to and already L-R document). Have you tried just installing a PostScript or TrueType font with Hebrew characters (as from here) and then switching from Latin font to the Hebrew font in your English document and typing the appropriate characters into the document?

[gabix]

1. Switch to Hebrew input.
2. Type in.
3. Done.

Also, try OOoFBTools, it has a virtual Hebrew keyboard.