To start off, open the document you wish to merge your documents into. This can be a new document or the file you want first.
Switch to the Insert tab. Click in the document where you would like the inserted files to go so the cursor is there. On the right-hand side use the drop-down on the Object button to select “Text from File…”
This will open up a file browse window for you to select the files to insert. You can select one or more documents. If you have multiple documents that you would like in a certain order, click the last document and then hold down Control and click the other documents in reverse order. You can also hold down Shift, click the last document and then click the first document if they are in order in the file explorer.
The documents will be listed in the correct order, left to right, in the File name field at the bottom of the Insert File window. After your documents are all selected, click the Insert button.
Your document will now have each document appended to the end, exactly as you specified. Save or Save As your document to retain the additional files being added.