One neat little feature of Quick Look is that if you want to copy some text from one pdf, rtf, or txt file (as far as I can tell, it doesn’t work with .doc and .docx) to another without opening the source file, you can browse through the Finder, hit the spacebar, and select the text from within the Quick Look preview.

However, if you find that you can’t select text inside a QL preview window, you may need to enable it in your defaults settings. To do this, triple-click the line below, copy and paste it into a Terminal window and hit ‘return’.

defaults write com.apple.finder QLEnableTextSelection -bool true