I am creating an extranet and the .doc .xls .ppt files are loaded and saved on the server in a folder ./folder/test.doc and on the extranet it is already shown that this file is registered, now the subject is that in an iframe only display the preview of the document, it does not matter that you can not modify it only if you see the 'preview' of the document.
As a complement to the answer, in addition to MS Office documents, .doc .xls .ppt is possible:
<iframe src="http://docs.google.com/gview?url=http://www.snee.com/xml/xslt/sample.doc&embedded=true" style="width:500px; height:500px;" frameborder="0"></iframe>
It is also possible to load PDF files:
<iframe src="http://docs.google.com/gview?url=http://fzs.sve-mo.ba/sites/default/files/dokumenti-vijesti/sample.pdf&embedded=true#:0.page.20" width="500" height="500" frameborder="2"></iframe>
As a limitation I would like to mention that documents that are protected with a password, it is not possible to inject this information.
With this simple iframe we can upload our documents to view them, accept Word, Excel, PowerPoint and other documents associated with Google Docs.
<iframe src="http://docs.google.com/gview?url=http://upgrade.com.mx/_docs/prueba.doc&embedded=true" style="width:600px; height:500px;" frameborder="0"></iframe>
Where
http://upgrade.com.mx/_docs/prueba.doc
is the document path on your server.