The only way I've found to get the Google Docs Viewer to work in an iframe is:
<iframe src="https://docs.google.com/viewer?srcid=[YOUR_FILE'S_ID_HERE]&pid=explorer&efh=false&a=v&chrome=false&embedded=true" width="800" height="600" style="border: none;"></iframe>
First you should go to your document on google drive :
You will get the code of the iframe you can use it to visualize your spreadsheet without the possibility to edit it
Try this tutorial-
https://www.youtube.com/embed/A5SkbcId-v0
U should have your answer.
According to Google Policy, if u like to have your document viewed with a iFrame, then embedded=true
should be in the URL.
Demo Code-
<iframe src='https://docs.google.com/viewer?url=https://docs.google.com/document/d/125CJmmlBfy7UgfYuBAmb1_HSCuyz8NV133361KTK1SE/export?format%3Dpdf&id=125CJmmlBfy7UgfYuBAmb1_HSCuyz8NV133361KTK1SE&embedded=true' frameborder='0'></iframe>
No, you can not, this parameter is specify that source would be embedded. And the idea behind using it is to avoid clickjacking attacks