Depending on your preference, you can use their iPhone fax app, Android fax app, email-to-fax service, or web-based faxing to send a fax without a fax machine.

For instance, if you wanted to fax something to 800-555-1212, you would send the document to an email like [email protected] (not a real address).

To fax a PDF, use a service that supports the Adobe document format such as FaxZero, MyFax or eFax. Each service allows you to upload a PDF and send the document to any fax number in a few steps.

The Mobile Fax Free app allows you to fax single-page documents for free. Mobile Fax Free will convert a picture taken with your phone's camera into a PDF document.

If you want to send a fax with your iPhone, you'll first need to have the document handy, either in a digital format like a PDF, or a physical paper that you can take a picture of. Either way ...