How to organize the viewing of office documents on the site?

Question

PHP

Good afternoon.
On the site (php) it is necessary to develop a view of office documents (doc, docx, xls, xlsx, ppt, pptx, pdf), documents are confidential, so google docs services cannot be used.
Does anyone have information in which direction to dig?

Answer 1

1. Not only public access is possible in Google Docs.
2. It is quite enough to install an extension for viewing in browsers and give the correct MIME when files are downloaded. Then the browser will display them itself.