Embedding Google Documents is straightforward. Simply open the editor then
Insert>Drive> ... and select the type of document you want to insert.
(See also Embed 'other' Google Drive files)
Alternative methods with slightly different results are explained well on Mori's site, here
Below is an example of Google Doc embedded using Insert gadget. Note that if you have editor access to the document, there will be an 'Open embedded doc' link at the bottom of the page.
(See here for an example of the same document embedded using an iFrame)