If you need to copy some text or even an image from a file, you don't necessarily need to open the file up in an app. Often Quick Look can be used to find and copy file contents.
Note: This is Club MacMost exclusive content. To view this video click the thumbnail below to go to the post as Patreon.com. Once there you will be able to view the video as long as you are logged into your Patreon account and a current supporter of MacMost at the "Club MacMost" or higher level.