First question is why do you absolutely have to fax? Are you just trying to send documents to a business or individual? If they have an email address, it sure easier to just scan a document in any printer with scan capabilities, save as a document on your computer and send as an attachment.
Yes, it can be done, but it needs a phone modem. From How To Geek...
Microsoft Windows even contains a Fax and Scan application that allows you to send faxes. The catch is that you’d need your computer connected to the phone line — yes, this means that you’d need a dial-up fax modem. You’d also need a landline telephone connection and you’d have to tell people to stay off the phone when you’re sending faxes, just like in the old dial-up Internet days. Of course, if you were faxing a lot, you could pay for a a dedicated fax telephone line — this might even be necessary if you were receiving a lot of faxes.
Another option is to go to some place like your library or UPS store. Some of them will send faxes for you for a fee.