Combine documents together

 
To combine documents:
  1. Open the document you want all your pages combined into.
  2. Open the other document. On the left where you can see all the page thumbnails, select all the pages by holding down Ctrl (or Cmd on Mac) and clicking on them, then press Ctrl + C (or Cmd + c on Mac).
  3. Return back to the other document. Hit Ctrl+v (or Cmd+V on Mac) to paste those pages into the new document.