A work-around for sending a PDF (or any kind of file) using ifax
1. Locate the file you want to include in your fax so you can view it on your iPhone screen
2. Press the iPhones on/off button at the top left of the iPhone at the same time press the function button ( thats the one under the "space" bar in your texting screen)
3. When you press them at the same time it will create a copy of what you see and send it (as if it's a photograph) to your photo album folder. 
4. When iPhone asks if you want to include a photo go to your photo album folder and "include" your new file in the fax as if it were a photo. Voilà!!! Works every time!!!!