|You need to think in terms of combining two documents, not two files (there's a subtle but important difference).|
Open one of the documents, select the entire content, right-click and choose "Copy".
Now open the other document, place the cursor under the last line of that document, right-click there and choose "Paste".
Save it (in two locations for safety), then you can delete the first document file you opened if you so wish.
message edited by phil22