This resource contains step by step instructions with screen shots to show how to convert a pdf file to a google document, so that it can be edited. Two methods are outlined. Method one converts directly from Drive and Method 2 involves downloading a google conversion app.
The steps are not difficult, but the benefits and time saving of this feature is worthwhile.
Note that this does not enable a perfect conversion. It won't work well with large documents that contain a lot of diagrams, tables, or graphics.