I have one question regarding search query string.. Does it matter? For example someone search on my blog " *.com/blog/search?q=social+networking" "social networking", but there is no info about that on my blog. Can search engines crawl this page as different pages on my blog? If yes than what about tile-meta of that pages..?
No search engines cannot find that page on your blog because it is not being linked to from anywhere.
Why do you think someone would download the file, view it, and then reply to your query. Better have the content in post.