I have dialog audio that was recorded indoors. What is generally the best way to make it sound like it's outside using and audio editor like sound forge, or even in vegas?
Definitely use outdoor BG's. You may be able to throw a small amount of reverb in if you pull out the lows and highs in the verb, but it needs to be really really subtle.
You can also "worldize" it. Pipe it into a speaker that is out side and rerecord it. Works really well in the right situation. Also a convolution reverb like Altiverb that has an outside IR can help.