Yes, there is online manual. You can use Adobe Reader to open the file. The Adobe application will automatically detect the file and enable the on screen controls to handle it (rotate, pan, zoom, etc). There is also a page set up by the Adobe Corporation to come in need for those that want to learn how to use it.
Access the help page here: https://helpx.adobe.com/acrobat/using/displaying-3d-models-pdfs.html
Tip: Send the file to your customer, and send the above link as well. Tell him to read the instructions on the page first and then open the model.